The process I used from stock HTC Hero to fully flashed (Talk, Text, MMS, Web, Market and Apps--GPS too) is quite simple.
Step 1) Use the official Android ROM upgrade utility from Sprint and upgrade ROM to stock 2.1
Step 2) Root ROM and get modified boot image:
http://forum.xda-developers.com/showthread.php?t=694572
Step 3) Apply correct PST settings:
http://www.howardforums.com/showthr...o-Flash-to-Cricket-with-Talk-Text-Wap-and-MMS (Be sure to apply the PRL as well)
Step 4) Flash DamageControl v1 (After creating a Nandroid backup)
Step 5) Boot into Android and get AnyCut and apply the correct proxy (wap.mycricket.com:8080)
Step 6) Flash Token's Cricket_v10.zip (This is for MMS and all that) NOTE: If I remember correctly, you have to download APN Backup and Restore first.
Step 7) (Might not apply to you) The APN settings as they were weren't working for me so I found this post here:
http://androidforums.com/htc-droid-eris/51990-eris-cricket-mms-wep.html#post432287
My APN Settings look like this:
Back up your APN. Use the above code, replace YOUR10DIGITCRICKETNUMBER with your number including area code then save it as an xml and restore it as your APN.
I'm writing from memory so I may have left some things out. This is a basic guideline of what I believe to be important points. This severely lacks detail but should be a good jumping off point for you. After I did this, my phone became fully functional. I have yet to find something broken. I did have to change my maximum MMS size to 500kb in order for it to work with most my contacts.
Good luck,
Jared