CM10 is now available.
From rooted stock or a custom rom, just download and install updated Rom Manager from the Play Store and download CM10 Nightly and GAPPS. Reboot into ClockWorkMod, factory wipe, disable signature check, flash CM10 twice. The first time partitions our tabs and reboots. Flashing a second time is for good measure. Then flash GAPPS. Done.
Note: I am not sure if Rom Manager can flash ClockworkMod directly. I personally updated from ICS > CM10 by downloading CM10 and GAPPS through GooManager and flashing manually in ClockWorkMod.
Its been reported that you can go directly from rooted stock to CM10. I've actually completed everything below to get to ICS first (Stock > ICS > CM10 JB).
CM10 is a much better experience. The tab works much better, doesn't freak out, lasts longer, plays better.
Wow. Lots of different, confusing, and scattered information about how to go from stock Gingerbread to the latest CM9 build. It is all very confusing and honestly most of the useful information isn't even on this site. So I figured I would help myself (and others) in creating a very detailed walkthrough of the process required to successfully get from GB to CM9 Build 7.
**This specifically outlines the methods to take a COMPLETELY STOCK Sprint Galaxy Tab 7" SPH-P100, unrooted, to a ICE CREAM SANDWICH rom. I "think" it might also work for the Verizon CDMA and a few others. I think the ROM itself is a general overall generic build for all 7" Gtabs. So heads up that if you have a different version, you might want to use this as a guide rather then a step-by-step.**
BACKUP EVERYTHING YOU MAY NEED BECAUSE OBVIOUSLY THIS PROCESS WILL FORMAT YOUR GALAXY TAB
We need to download Heimdall's App and his Drivers (Main URL). This is the first confusing steps as everyone suggests using an older version, but the included drivers don't work on newer Windows OS's. So you have to mix and match a few different versions to get it working. I've already compiled an archive with everything you need: Heimhall Mixture /w zImage & ClockWorkMod 126.96.36.199
1. Extract everything to a simple folder [ex. C:\GTABICS ]
2. Turn off Gtab. Hold VolDown+Power until you get to a downloading screen
3. C:\GTABICS\Drivers\zadiag.exe to load drivers [try running as Administrator]
4. C:\GTABICS\heimdall-frontend.exe to start the process
5. Kind of confusing. Focus on the "BROWSE" buttons. Look for "Kernel(zImage)" on the left and "Recovery" on the right. Hit browse for each one and select the appropriate file from C:\GTABICS. Obviously "Kernel(zImage)" = "zImage" and "Recovery" = "recovery.bin".
6. Make sure Kernel(zImage) and Recovery both have files selected and a checked box. While GTAB is at the black Downloading screen: Hit "START".
7. The process is pretty fast. Don't rush. At this point your tab will probably just bootloop anyway.
LET'S GET THIS SHOW ON THE ROAD
Now you have ClockWorkMod installed and a proper kernel, most flashers will feel really at ease right now. But there are a few little quirks that will cause this to go bad. You have to install 2 versions of ICS to get to the latest; One using the existing partition table, and a second that will update to a newer format. You obviously have to install GAPPS like always with a CM rom, but not so fast, you have to manually "MOUNT /SYSTEM" in CWM before it will even take. And there is the fact that you have to manually open and edit the CM9 Build7 update and remove code....[holy crap].
But it is pretty easy once you go through it once.
JT1136 CM9 V5
JT1136 CM9 V7 UPDATE
Prepare CM9 v7 Update
1. On your PC, open "update-cm-9.0.0-RC0-galaxytab7c-KANG-BUILD7.zip" and browse to META-INF\com\google\android
2. Copy "updater-script" to your desktop and open with Notepad and remove the first 3 lines or just Download it.
3. Drag and drop the update-script back into the META-INF\com\google\android folder, overwriting the existing one.
If all goes well, you are now done with the PC.
COPY FILES AND FLASH
1. Copy Build5, the new Build7, and GAPPS to your microSD card.
2. Boot into ClockWorkMod: Power off. Hold VOLUP + POWER
3. Factory Reset / clear cache / wipe Dalvik Cache / Breathe
4. Flash zip from SDCard: locate Build5 and Flash
5. Factory Reset / clear cache / wipe Dalvik Cache / Breathe
5.5 [OPTIONAL] You should be able to boot into ICS at this point if you want to make sure build5 flashed properly before upgrading to build7
6. Flash zip from SDCard: locate Build7 and Flash
At this step, my GTab rebooted in the middle of the process the first time. It freaked me out but I assume (now) that since it changed the partition tables, it needed to reset. So I did it a second time just to be safe:
7. Flash zip from SDCard: locate Build7 and Flash
8. Factory Reset / clear cache / wipe Dalvik Cache / Breathe
Congrats. You should have a working bootable CM9 build. But lets flash GAPPS so we have our Google services. This is tricky.
9. Mounts and Storage > Mount /System
10. Flash zip from SDCard: locate GAPPS and Flash.
11. Finally [!] reset device and prepare for boot.
Now you are on the latest CM9 build  and have the latest GAPPS installed. Hopefully you are booting now and see the famous ICS Boot Animation. Have fun. In the future you should be able to simply download new roms as they are available and flash normally like you would any other device.
Drivers and Flash Tool
Convert to Sprint
The above procedure will set your Tab as a Verizon version. If you plan on using the Sprint cellular service or just want everything to match, then flash this via ClockWorkMod.
I didn't do any development work. All credit goes to Heimdall for his fantastic Recovery Flasher and jt1136 for his great stills porting this awesome rom over to our Galaxy Tabs. All I did was bump and grind my way through to see a successful working flash. I figured if I didn't post a walkthrough here, I would hate myself in 6 months when I boink something up and have to do this all over again. I would recommend you keeping all of the files safe somewhere to prevent this headache again.
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