Those sites are going to be awesome for finding info and parts. You got one of the better years of cars for the Fox body. I personally like the 93, but that's just preference. It's pretty much identical. Your 90 can only have a few of the "common" problems, because of all of the changes. For example, you have the Mass Air Flow system of fuel injection, as opposed to the 88-earlier system (possibly some 89s) which used Speed/Density. Being a 90s car, you might have the T5W (world class) stock, which is a stronger trans compared to the "regular" T5.
Driver seat usually goes "ghetto" (the right side will start to recline and bend backwards, compared to the left side).
Clutch cable adjuster (quadrant) strips and you have no more clutch pedal.
Lower ball joints (stocks suck)
Ashtray door won't stay closed ($4 fix using a spring)
Power window/ lock motors burn out (easy to replace)
Stock radio is horrible
That's just the insignificant stuff off the top of my head. And, it's all stuff that's easily fixed, as well as cheap. Fox body Stangs have probably one of the best aftermarket following of any car. As long as you have a decent chassis, the rest is cake.