You can't judge a book by its cover and, generally speaking you can't judge the internal condition of an engine by how it looks on the outside. Many years ago I purchased a junk yard Buick 455 that was covered in grease and mouse fur. I gave it a tune-up and a cosmetic cleaning with foamy engine bright and a can of Buick engine red spray paint, tossed it in my 72 Riviera and fired it up. That engine turned out to be the best 455 I've ever owned! The fact that your engine is complete and together is a very good sign. Be prepared to see a lot of crap in the VOD. Dirt and debris tends accumulate down there. The junkyard soured 84 Volvo 760 engine that I recently installed had a filthy VOD, but it runs like a champ and has ample power.
From a durability standpoint, the PRV is a decent engine with documented examples logging over 200K miles in a few DeLoreans and many Volvos. However, like any other aluminum engine, they don't like to be overheated. Thus, you could see a nasty looking PRV with 175K on it that runs like new, but you could also see a 5K spotless engine that is internally trashed from overheating. I've also noticed that PRV's like heavier weight oil. I previously ran 20w50; however, I recently switched to 15w40 Delo for the higher ZDDP levels.
Also, make sure you plug every spark plug, fuel injector and intake opening before blowing any compressed air on any parts. The oil in the intake is a sign that the turbo seal may be failing, but it is not necessarily a sign that the engine itself has internal problems. The blow-by that is a concern is not the blow-of the compressor seal to the intake, but rather the blow-by of the piston rings into the crankcase.
For an interesting thread which includes an extensive clean up of existing k-jet parts, you might want to take a look at the documentation of 11114's restoration from a few years back:
http://dmctalk.org/showthread.php?35...-from-the-dead
While engine swaps can be fun once they are done, they often quickly turn into a project car spiral. Dave of Project Vixen described it better than I ever could:
http://www.projectvixen.com/week244.htm