Rear slider, easy. Lay slider down. Put gasket around it. Use 1/4" nylon rope, hook tool, and glass cleaner as lubricant. A second person on the outside holding the glass and slightly pushing will help. Once you get good, you can do it yourself in 5min, or less. (Note: If your gasket has chrome or rubber "interlock", toss it and get a new gasket without. They look ugly and don't install as easy.)
What specifically is your "power window" dilemma?