There are two approaches to replacing windows -- make the window fit the opening, or make the opening fit the window. This is an important distinction when dealing with non-standard size window openings. I'm a good woodworker, and would be quite comfortable re-working the opening to fit a standard size window - but I prefer to make the windows fit the openings, even if it means spending a bit more on the windows.
A few things to remember when replacing windows -- get rid of any rotten wood while you're at it... don't forget your insulation/caulk, and be sure to install them square, plumb, and level, hehe.
As to brands - Pella and Anderson windows are both excellent brands, and easy to find at most building supply stores.
For the insulation - I prefer to use batten fiberglass insulation to fill large cavities, followed up with DapTex insulating foam. DapTex does most of its expansion immediately - an important factor. It also cleans up with soap and water. Great Stuff is another popular brand of insulating foam - BUT - it can continue to expand up to an hour later - which means you can actually put your window frames in a bind... and as anyone who has ever gotten it into their clothes, or on their hands can tell you - its a royal pain to get out, lol.
Before installing the new window, I would add a wind barrier around the opening, to at least a foot beyond (simply a layer of plastic).
I like to 'dry-fit' my windows, before caulking, just to make sure there will be no problem getting it in - takes a little extra time, but can save a big mess if there happens to be any problem, hehehe.
It takes me about an hour to replace a standard window, start to finish, but I've had a lot of practice, and have all the necessary tools.
By the way - if you choose vinyl windows, do NOT use an oil base lubricant on them (even most 'silicone' lubricants are oil base). The oil will 'attack' the vinyl, causing it to become brittle, and prematurely age. Vinyl window manufacturers recommend that a wax product be used to lubricate the windows. Johnson's furniture WAX (not 'polish') works very well, as does the Gulf brand wax 'cakes' (found anywhere canning supplies are sold, and at hobby stores).
After installation, you may find it necessary to adjust the spring mechanism in the windows. Some brands make a special tool to make it easy to do this... if the brand you choose, has such a tool, go ahead and buy it, you'll appreciate it later, hehe.
Good LuckHow difficult is it to install replacement windows doing it yourself?Go ahead you can do it. I ordered one window from Home Depot to try it out for the first time it took me two hours no problem. Then I ordered 18 more and put them all in over the weekend including the picture window and door wall.
