I'm doing a little research on 1999-2002 GMC 1500 or 2500's to figure out what I should be looking for before purchasing one.

How does the 5.3L compare to the old 5.7L?
Is the 6.0L a better choice than the 5.3L when it comes to reliability?
Are there common engine problems with the 5.3 or 6.0 engines?
Any common module/computer/sensor problems?
What things should I look out for (specific to the GMC trucks) before buying?

Any tips hints or warning would be greatly appriciated especially from GMC truck owners themselves. Thanks.