172 is a fine aircraft. Probably the best thing to know about it is
it's history. If it's had an engine rebuild what is the quality of the
rebuild? Make sure you pay YOUR mechanic to do a compression test,
preferrably while the owner is elsewhere, and be objective about what
you have. There are lots of 172's around. Also it is more cost
effective to buy the airplane with the avionics you want rather than
planning on upgrading. Paying a little more to get what you want will
be worth it, as the hourly costs outweigh the aquisition costs in only
a few years.

As for the pilot fatigue issue, if that is a problem, get some noise
cancelling headsets. They are really great.