The "update.zip" file you used to root the phone should be kept in a seperate folder. Don't keep it in the root of the sd card. When you install clockworkmod it will overwrite the "update.zip" file you used to root and replace it with another "update.zip" which will take you to clockworkmod recovery if you ever bootloop or brick the phone.
How it works is that you hold power and volume +; - keys all at the same time to get into standard recovery, then you choose apply: update.zip, which will then take you straight to clockworkmod, from there you can restore the image you hopefully backed up before trying to mod your phone.
As for selling the fascinate, I'm right there with you, I have a desire fully rooted/s-off/etc... there is so much support with it and there is literally nothing with this phone, and you know what? I like this samsung better form factor wise and screen size, but software is really behind. (2.1, touchwiz, etc) I installed launcher pro, and beautiful widgets so it looks like HTC sense, so i'm not unhappy, but its definately a bit slower than my desire with 2.2 and the desire HD rom running.
If I sell it, i'm 100% going to get a nexus S, as I really like the form factor of this phone, also, compared to the bell vibrant, the build quality is better with the Telus SGS.