For repair and weatherization of historic steel windows, see the article on Historic Steel Windows Repair, Restoration, and Weatherization.
A Middle Way to Save Money: Do the easy things yourself, and hire a contractor for the rest.
Here are some references:
Do the simple things first. Maybe they will be enough!
When the simple things are not enough, then hire a skilled contractor.
CAUTION: Window companies will advise you that your windows cannot be repaired and are energy inefficient. Their advice: you need to buy their new windows! DON'T BELIEVE THEM!
Employing contractors always is tricky, for two reasons.
Advice. Know what you need and how it should be done!
Here's how: Spend time studying the DIY information so you understand what you need contractors to do and how they should do it. With this knowledge, you can keep looking for contractors who know the right thing to do and how to do it right.
Disclaimer. The window repair and restoration contractors listed here have credentials for windows and have been recommended by building owners in Historic Districts. Neither the Historic Boston-Edison Association not the Detroit Historic District Commission can guarantee your satisfaction with any contractor. Every owner must find contractors with whom they can work satisfactorily. Check their references yourself.
H & R Window Repair Company
Allstate Glass Repair
Windows Diverse Services