How to root manually/without Windows
There is already an excellent write-up on how to use SuperOneClick to root your Optimus V.
Unfortunately, you may not have a Windows machine available to run the util, or your PC hates the LG drivers, or you may wish to control how you go about rooting your device.
Hence this short write-up which, obviously, relies on pieces I got from that other write-up.
I. Rooting your device
1. You still need ADB!
2. Download the LG Optimus V Tools package from http://nexus.zteo.com/projects/tools/
3. Unzip it
adb push psneuter /data/local/tmp/
adb push su /data/local/tmp/
chmod 777 psneuter
chmod 777 su
5. You should be kicked out of the shell
mount -o remount,rw -t yaffs2 /dev/block/mtdblock5 /system
cat /data/local/tmp/su > /system/bin/su
mount -o remount,ro -t yaffs2 /dev/block/mtdblock5 /system
(Oh look you are root!)
That's it. You now have permanent root access.
After rebooting your phone, adb should be back to logging you in as a regular user but typing "su" will do the trick.
Note: I realize that the version of SuperUser.apk that comes with SuperOneClick might be re-usable here. I haven't had any success with it but you may.
II. Flashing a new ROM
1. After rooting your device, obviously...
2. Get an image for the ROM you wish to flash...
Currently, my favourite one is a fairly recent version of Zefie's CM7.
You can find it by googling "update-cm-7-04282011-NIGHTLY-thunderc-Xionia-signed.zip" -- I will refer to it, below, as <your_rom_zip_file>
3. Get a minimum Google Apps package for flashing as well.
Here, I would google "gapps-gb-20110325-signed.zip" -- I will refer to it, below, as <your_gapps_zip_file>
adb push flash_recovery /data/local/tmp/
adb push recovery.img /sdcard/
adb push Debug-FormatSYSTEM.zip /sdcard/
adb push <your_rom_zip_file> /sdcard/
adb push <your_gapps_zip_file> /sdcard/
chmod 777 /data/local/tmp/flash_recovery
4. In recovery: Flash Debug-FormatSYSTEM.zip
5. In recovery: Wipe cache and dalvik-cache
6. In recovery: Flash <your_rom_zip_file> -- this will take a while
7. Do not reboot!
8. In recovery: Flash <your_gapps_zip_file>
9. Now, reboot.
10. Let your phone think about life for a few minutes
11. Select "Skip" when your phone asks you to create/enter your account info
12. Launch the market; now, enter your main account information