Easy to change hboot.
First I would recommend making a nandroid
Next dl and flash a rom that will boot with most hboots. I choose harmonia for this.
Once harmonia is running on your phone, download the pg86img.zip of the hboot you want, for jb you're gonna want 1.50.5050.
Move the pg86img to the root of your sd and reboot to bootlader.
Accept the update, and reboot to the rom.
Now make sure to go and move or rename the pg86img.zip NOW, if you forget to do this, you may end up pulling some hair out of your head. Just move it and be done.
Now I would suggest making another nandroid. With a nandroid of harmonia, you can restore no matter what hboot you are on, and will save you frustration.
You are now all set to find and flash any jb rom you want.
Make sure to check out the roms for the evo 3d cdma as well. DO NOT FLASH A GSM ROM