I previously owned an E34 540/6, and it was an exceptional car. Excellent build quality, absolutely night and day compared to my E36 (crap). One of the last overbuilt BMWs. Great to drive, great power, great handling. Can you tell I loved it?
That's a good price, if it is as nice as described. A friend of mine just sold a nearly perfect E34 540/6 for a bit over 10k, I think it had about 110k on it, and the newer Alusil motor. Here's a good run-down on the Nikasil issue:
http://www.koalamotorsport.com/article-m60v8.asp
The entire problem was excessive sulfur in SOME US fuels eating the Nikasil liners in the M60. This problem affects ALL M60s, the newer Alusil blocks weren't introduced until 1997. If the car still has a Nikasil block, and passes leak-down, it will be fine. Newer fuel standards mandate lower sulfur, so it's a non-issue today. In 1995, sulfur levels varied from fuel to fuel and state to state, so many cars were not affected. My 540 had 135k on the original Nikasil, and it ran like new. Many M60s with rough idles were mis-diagnosed as Nikasil problems when they really were suffering from intake leaks, so the problem seemed worse than it really was.
Bimmer.info is E34 heaven, there are some real tech gurus on there. Bimmerforums has some good information, but you have to wade through the 16 yr old BS. Big issues are suspension bushings wearing out (shimmy at 55 MPH), requiring a total rebuild ($500-$1000 parts), intake gaskets and PCV plate leaking and causing a rough idle ($100 DIY), seat cable leading to uneven power seat adjustment (free), and misc interior issues. Overall they are great, rare cars, if you find a good one you won't be sorry.