If you're patient, you can usually pick up a used motor in the 150-hp range for $1500 - $2000 and get it put on for a couple hundred more. Just keep scouring the internet. You may have to bring home the boat that's attached to it, too, but you can sell that out on ebay for a few hundred to some poor schmo who put a tree through his boat.
Blown power heads usually result from repeated long full-throttle runs combined with poor cooling - either a bad impeller, clogged inlets, motor too high on jack plate, etc., which may not always trigger a pressure alarm until it's too late. 95% of blown motors are operator error either in maintenance or just running it harder than necessary. Not making judgments on you, but that's been my experience.
I would probably avoid rebuilding as it usually ends up in countless trips back to the shop for adjustments, etc. Just ask the shop where is a good place in your area to start looking for motors and start hitting the net.