How To: Flash a New Recovery Image
http://theunlockr.com/2009/10/15/how-to-flash-a-new-recovery-image-if-you-are-already-rooted/
. Flash a New Recovery Image
1. Find the recovery image you want and MAKE SURE IT IS FOR YOUR PHONE (should say in where you download it what phone it is for).
2. Write down the filename of the recovery image EXACTLY as it is written (i.e. RA-Hero-Recovery-v1.2.2.img).
3. Put the recovery image file on the SD card (not in any folders).
4. Download Terminal from the Market if you don’t already have it and install it (there are a few different terminals in the Market some have an onscreen keyboard and some don’t experiment till you get one, also hold down Menu in some of them to bring up the onscreen keyboard if you don’t see it).
5. Open the Terminal program and type the following (with hitting enter at the end of each line):
su
flash_image recovery /sdcard/name-of-recovery.img
flash_image recovery /sdcard/name-of-recovery.img
6. In the above text, replace name-of-recovery.img with the name of your recovery image (make sure the .img is on the end).
7. Phone should pause for a second and then show you a new blank line. Turn it off and back on by holding down Home and Power to ensure it flashed correctly. Done.