So my mustang only has mechanical seats, and i found a good pair of nice leather ones for 100$ each, is it possible to wire the new seats up? If so, how difficult is it?

 

If the harness is there it's not hard at all although you may need to hard wire the seats like I did when I put 03 seats in my 95. However if it's not, good luck figuring that out.

 

By harness, you're referring to the harness attached to the replacements seats themselves?

 

On my 2000 and 2012 all of the switches are in the seat, I think all they need is power and ground, they may not even need a ground as they are grounded by the bolts that hold them in. What does the connector look like that connects to the car's wiring?
btw, if the wiring harness for them is installed, you will probably find the fuse slot for them is empty, It's either a 25A or 30A, your fuse panel should say on it.