If you have a phone shipped with ZV6 then go straight to the 2.2 root guide and get the "lite" zips. If not then find the lgnpst guide, do that, then go back to the 2.2 root guide and use the "lite" zips. To check try going into terminal emulator and typing "reboot bootloader" if it reboots to a blue screen you have fast boot, if not you need to downgrade to get it. If thats too much, well good luck and i hope you never need fastboot. You can remove /system/ect/install-recovery.sh to get the recovery to stick.
ROM Manager/Clockwork recovery dont do well with the ally. Also you may want to do some searching becuase EVERYTHING you want/need to know has already been discussed more than once and there no point to start another thread when you could just post on an existing about the same subject if you still have questions.