I was the original poster and I know that several people also had questions about this.
What I've found out - there are as many window tint, gas fill, style, etc, options as there are opinions as to what is the best!
There are 3 options when replacing windows - 1. leaving the frame and replacing the sash and window panes; 2. replacing the window (pull out the old and the window slides in) and then 3. a "new construction" window (tear out the window and everything around it before replacing the window).
Here is a good brochure that describes the three options:
http://www.finehomebuilding.com/how-to/articles/get-right-replacement-windows.aspx
Option 1 is definitely the cheapest installed for us - quotes are $6500-$8600 installed - 19 windows (9 72"h double, 1 triple - thirty windows in all); However, for this option we have not been able to find a dealer for us to be able to do it ourselves.
Option 2 - windows that qualify for the tax credit have been quoted as only about $400-$600 more, so that's what we'd do. Our quotes for windows alone range from $5800 - $6800 (Single hung with no grilles). Quotes for labor and haul away range from $3000-$4000. We can do these ourselves too, but more costs involved in renting scaffolding for our second floor windows and finding a place to dispose of glass panes (recycler will take the alumin frames and we don't have to scrape the caulk off - just 5 cents less per pound) (No glass recycler around here - 2 hour drive).
Option 3 - not an option for us at this time.
Also, on
youtube there was a "tool" that someone developed to help remove the old frames (for Option 2 above). Can't find the link now.
So, this evening we have another contractor coming to bid.
We should make a decision this weekend and hopefully have new windows by the end of March.
Hope this information is helpful to someone.