Well the first thing you should have done was to tell them NOT to give you the OTA otherwise they can keep the phone, they dont have to give you the OTA and you didnt have to accept it, that's of course too late now but for those who have to replace, keep that in mind.
That said, you are now pretty well out of luck until the boys at revo. come up with a fix or are able to completely get around the 1.5hboot and fully root the phone..
You will be able to flash twrp, you can flash roms, there are success stories of this even while using the HTC unlock method. You can read up on the xda htc evo 3d General forum for what is and is not currently working.
the best advice would be to WAIT and DO NOTHING and TURN OFF ANY FURTHER OTA updates: Settings, System Updates, HTC software update and UNCHECK scheduled check.