Another option is a used motor. I've replaced a lot of motors over the years for customers and friends. The one thing they had in common was no matter how well the motor ran, most of them sold the car within 1-2 years. When I asked why, they all said something to the effect: "It was running fine, but I just couldn't trust it, so I sold it while it was running well."

The easiest and least expensive thing to do is to install the same year used motor. This will give you, IME, the best chance of recovering your money later.

I don't know anything about these guys, but near the end of their ad they list used prices for various motors:

http://cgi.ebay.com/ebaymotors/Porsche-01-Boxster-3-2-3-2L-Complete-Engine-Motor-72K_W0QQcmdZViewItemQQcategoryZ33615QQihZ006QQitem Z160139973056QQrdZ1QQsspagenameZWDVW

I've seen cheaper prices at other yards.

Maybe Int. Shaft Bearing Failure
 

Sorry to here about your problem.
Sounds like possibly an Intermediate shaft. When it happened to my '03 at 27000kms. the engine didn't quit but when I stopped to check because of a change in engine tone I noticed it dumping oil on the road . The diagnosis was an int. shaft bearing failure which in turn cracked the housing, thus the oil loss.
The engine was replaced with an '04 but fortunately I had an extended warranty and extra lucky because I live 400kms from the nearest dealer and the trucking cost alone to and from was about AUD 2000.
Good Luck,
Glenn

993's had the 3.6L.

Yes, as did the 964's, but you can't put that one in your boxster ;)

oh, because it's air cooled?

You are correct sir!