You can find a rebuilt in engine for around $1500 if you look around or a junkyard deal even cheaper. Remember you will also need a transmission and other parts. The problem is having someone install it. If you can find a shop to do it you are going to pay big time, around $80/hr or more. You'll have a few grand easy wrapped up in just the install. If you can find through word of mouth or have some friends who are good at custom work you will get it done cheaper. For example, I've done a V8 Ranger swap for a person already. In a few weeks my fiance's cousin and I are doing a S-10 V8 swap, in this case for my own grandfather; he even got wind of the good work we do.
Matt