If you are stuck in traffic a lot, automatics are nice to have. Gas mileage is slightly better on a 5-speed, but not by much.
On gen3s (1992-1996) timing belt replacements are recommended every 60K miles.
On gen4s (1997-2001) timing belt replacements are recommended every 90K miles.
For detailed EPA estimated mileage figures, just go here.
http://www.fueleconomy.gov
I have a 2000 LE Automatic with 4-cyl engine. I get about 26-27 MPG in mixed city/hwy driving.
To get the timing belt changed, figure low $200s just for the timing belt job for a 4-cylinder, more for V6. However, depending on what else you may need to have serviced in the same area at the same time (like water pump, cam seals, front main seal, etc..) prices go up from there.
It has been a very cheap car for me to own. Aside from regular maintenance, I think I replaced 1 sidemarker bulb and a gas cap o-ring.
I would recommend 2001, that was the last year of the gen4 Camrys. However, do take into consideration of the condition of the car and odometer mileage.
If you're concerned gas mileage, get the 4-cylinder.
What is your budget anyway?