New to the mysteries of subarus

[Turbofishy]

Hey I just purchased not only my first subaru but also my first manual. Its a 1998 subaru legacy outback with 170k on it. My last car was a automatic saab 9-5 and I did do the maintenance and a few of the minor repairs on it. I would really like to do the same with this vehicle along with doing a few modifications, like a short throw shifter, braided break lines and some power upgrades if possible. Mainly my questions are whats the best place to get good parts online aftermarket and oem, some good ways to add power, whats the best repair manual around for my vehicle, and how do I tell what motor I have?