Welcome Jessica!!! I've been here for a few months and have become addicted. Is there some sort of support group for this? LOL
Mr 5 0 is very right is what he is tell you for first mods. I would suggest picking up subscriptions to some of the more popular Mustang Magazines
Mustang Monthly (my personal favorite)
Mustangs and Fast Fords (Also an awesome magazine)
5.0 Mustang & Super Fords (for all your mod questions)
These will teach you a lot about the Mustang in general and also give you some good Ideas on modifications that you would like.
See ya around,
Shelby