Help Kayle's Grand Am

[TheEdgeofSanity]

well, my friend Kayle has a 1999 Grand Am with the 2.4 and its having some issues. she (being a girl who's all about appearances) is embarrased of her car because it doesn't run very well. i told her that i would look at it and see if i could get it to run a little better but i have no clue on where to start with a 2.4. I want to do a tune up including spark plugs, oil change, air filter change, and a tire rotation. I'm not screwing with the coolant because the car has never over-heated. Anyway, am i missing anything? also, how do I get to the spark plugs and what kind of oil filter does it take. p.s. the car has 116,000 miles and the original spark plugs so i think its due for some maintenance.

symptoms that car is having:
shuttering, rough idle, hesitation, slow acceleration, takes alot to start (she has to pump the gas pedal)