Windows - try cleaning the switch contacts first, especially the drivers door switch console, here's a write up on it. I did it when my driver window got stuck and they were black, cleaned them and all'
good since.

GM Power Window Switch Copper Contacts Cleaning Guide - 1997 to 2003 Pontiac Grand Prix & W-Body Sedans Maintenance Instructions


LIM's are good if there's no evidence of leaking. Otherwise, it's worth a few hundred to replace all the gaskets and clean everything while it's open (TB, SC) Plugs/Wires, Coolant, Tranny Pan drop.

I've seen my older GP eat front hubs, but that was before I got into fixing my cars once again, can't trust these Mechanics these days, lol, no offense to anyone, but I'm sure they were using the cheap stuff I also saw some sad Balljoints on mine and changed the LCA's and BJ's on her... Rides like a dream now.

Welcome aboard and don't forget the pic's... we like pics!