1. In terms of service in the car like oil/filter changes, spark plug changes, what is easier a 3800sc or a 350LT1.
Probably about the same, but the Fiero is quite easy to drop the cradle for major work. The entire drivetrain comes out as a unit. You might also make an access panel in the cabin wall if you are so inclined, or use a remote oil filter, yada, yada.
2, There have been a couple of mentions of the 84 Fiero being a model to perhaps avoid. Why is this?
Aside from the Indy model, 84's were only available as a bumperpad coupe with a 4 cylinder. The electrical system is different as mentioned. The cradle is slightly different and has no provision for v-6 mounts. Fuel pump, instruments, etc are all made for the 4.
If you are swapping, then most of these will be addressed in any case. The 84 tranny case is slightly weaker and the 4 speed is available as a 4:10 final drive or a rare 3:32 option. The 3:32 is popular with the v-8 crowd.
84 models are far easier to find cheap..................
3. What is the weight of the LTI (4 barrel) versus the 3800sc. Power to weight is perhaps more important than just power. More weight on the rear for handling has to be a bad thing.
Don't know, but I doubt the difference is enough to worry about. Pick the motor you prefer.
4. Are there any years which are exempt from the emissions testing that are good for engine swapping.
My 86 is as well and 87 should be next year. The 88 models will not become exempt as I read the rules.
5. Is any particular Fiero model year better than another for engine swapping.
6. Any particular year better for suspension Mods.
88's have an upgraded suspension. Noticeably different in stock comparisons. However any 20 year old suspension will need attending and upgrading the earlier stuff makes it fine for regular use. The biggest point is the 88's have a solid mount cradle. Poly or aluminum makes a big difference in earlier cars. You can even weld plate in and bolt the early cradle directly if you wish.
7. Any particular year the 3800sc was a better engine?
Not rebuilding, obviously as new as practical. The GTP has more useful pulley setups and pcm AFAIK. Series 1 is cool

Feel free to pick on me, everyone does and it's good for the soul.

8. Would the Chevy LT1 be easier to plumb for exhaust?
Shouldn't be a big issue either way in deciding which to use. It's just something that has to be done and consists of the same parts.
9. Is a notch back easier to do engine transplants with?
No difference, except it looks more cool than a fatback

10. what does 4T65E HD mean?
GM auto tranny names are pretty standard
4 # of forward speeds
T Transverse (also L Longitudinal)
65 Model
E Electronically controlled shift
HD Heavy Duty (dguy thinks it stands for Hardly Davidson

)
You see that you'll get lots of different opinions. The best bet is to decide what you want, how much $$ you want to throw at it and go from there.
The important part is to get as good a donor as possible as a thrashed car will need just about everything replaced. At least the parts you'll use..... Look for rust, rust, rust and maybe lots of rust!!!!!
Gary