ok so first lets get you into recovery.
1. download amon ra 2.3 (the preferred recovery) from here:
http://androidforums.com/evo-4g-all-things-root/259446-clockwork-amon-ra-pc36img-files.html.
2. erase the "_ra2.3_" part of the name so that it is named PC36IMG. if you are using windows (it hides extensions) make sure not to add ".zip" to the name or it will look like PC36IMG.zip.zip.
3. xfer the file over to the root (no folder) of your sd card. this is the difficult part because you cannot connect your phone to the computer. if you have a card reader, you can transfer the file over that way.
4.go into hboot and it should automatically scan for the file and then press vol up to update.
now you should have a custom recovery and from there you have access to your sd card and you can just dowload a custom rom, xfer to your card and flash it from recovery.