I have a 98 Lumina LTZ with a 3.8L engine and have had only minor problems with it. I have 103,000+ miles on it and only had to do the following repairs, other than normal maintenenace items like brakes, rotors etc.
- Alternator failed at about 70,000 miles
- A/C compressor failed at 102,000
- power steering pump failed at 100,000
- belt tensioner replaced at 100,000 due to whining noise
- A/C condenser needed to be replaced due to leak
I expect it to last another 100,000. The 3.8L engine is very reliable in my experience.
Good luck,
Mark