Sounds to me like you need to focus a little. No point in shopping for motors if you don't know what, if anything is wrong with yours.
You mentioned you've got a mechanic buddy, get him or any mechanic for that matter to diagnose your motor.
Once you know what's up, go from there.
Then work on pricing out solutions. Like Baldamish said check out the machining prices, then rebuild kits based on your needs, wants, and finances.
I've been looking into it myself for a while. I was going to make a move months ago, but my motor is still running strong. I'm waiting for the inevitable, or a pile of money to fall into my lap.
Here is what I came up with. GM crate; price, professional build, and warranty and service convenience. You can't beat that combo in my mind.
However, if my mechanic buddy has the time, I will get him to rebuild the motor while I look over his shoulder. I REALLY want to learn, but I don't want to do so at the expense of an unreliable motor (doing it myself). It sounds to me like you have this option as well. I'd take it.
As for which motor. Price usually dictates, I'm going 383, unless a 400 enters the picture. If it's going to be a GM crate then either the HT383 or the Ram Jet 350 which you might be interested in (injection).