Screw ROM Manager. Do it this way.
Download this and put it on the root of your sd card. (Root meaning not in a folder)
3.0.2.8 recovery.img
Then download this from the Market. (Its free)
https://market.android.com/details?id=jackpal.androidterm&feature=search_result
Then open the terminal emulator you just downloaded off the Market and type this in:
su (hit enter)
flash_image recovery /sdcard/ x.x.x.x recovery.img (Hit enter) (**x.x.x.x, type in the recovery img's name dont type it in as x.x.x.x)
exit (enter)
Now you have clockworkmod recovery on your phone.
Now go to the PlayfulGod link I gave you and download those 3 links I told you too. And put them on the root of your SD card.
Reboot into recovery by turning the phone off and while holding the send key and the volume up key and tap the power. You will then go into recovery mode.
Once in recovery mode, scroll down to "Advanced" then to "back up and restore" then choose "backup"
Once thats done hit your back key so you are back on the main screen. Go to "wipe data/factory reset." confirm it.
"Wipe cache partition". Confirm it.
Go back to advanced and select "wipe dalvik cache" Confirm it
Hit your back key and go to mounts and storage and format everything EXCEPT your sd card. Sd ext is okay to format but do not go format sd card. It will erase everything off your sd card if you do.
Then go back to the main, and go to "Install zip from sd" then to "Choose zip from sd" and select the ROM you choose and confirm it. It will them flash your phone.
Once thats done go back to "Choose zip from sd card" and flash the Gapps file.
Once thats done hit your back key so you are back on the main, and go to "advance again and select "fix permissions"
Then hit your back key and go to the top and select "Reboot device"
Your phone will reboot and you will have Gingerbread on your Ascend. When your phone reboots you will have to put your Gmail account info in and then your done.
You will have no metroPOS apps and you will have to redownload any apps you had before. When your phone reboots its basically going to be a brandnew phone without jack on it.