what kind of windows do you have now? if you have older wood windows,
then replacement windows are an option. they install by removing the
sashes from existing windows, and allow you to save your existing trim
inside and out. you lose some glass square footage, but they are a
the best way is to remove the old windows sash, jambs, trim and all and
replace. no replacing windows is not terribly difficult, especially if
they are not real big or real high. usually re trimming them is more
work. you should have some basic carpentry toos, including a chop saw.
kinda depends on what kind of windows you have now and what kind of
siding you have. you'll definitely want to read up. preventing water
intrusion is critical.
vinyl replacement windows and vinyl windows are custom sized--whatever
size your rough opening is, you can buy a vinyl window to fit. but a
lot of people would say they look cheap and they are not as durable as
the best windows are probably aluminum clad wood from a manufacturer
like marvin or anderson. they are sold in stock sizes which usually go
in 2" increments. sometimes you have to do some remodelling to get a
stock size to fit your opening.
where you get them depends on where you live. they are sold at home
centers, lumber yards, glass companies, etc. try the yellow pages.