My 90 coupe deville has a broken drivers seat. I've tried looking everywhere except the dealership so, my next plan is to remove the seat and try to get the metel part that broke welded but my problem is that i don't know how to get the leather off so when the weld job is done i can put the same leather back on.

Seat tracks bolt to seat bottom frame, you may not need to remove cover. Once seat it out and upside down you see there is not much to it. If you have to remove cover you will need fasteners called hog rings and pliers to install them.