The following is a post from July last year regarding New Construction, vs Remodel/Retrofit windows. To clarify the post further, I call windows that fit completely within the window opening, requiring exterior trim, a remodel window. Windows with the built in exterior trim fin are Retrofit. The windows with the thin flange with the nail slots in the flange are New Construction.
Provided the fasteners holding your existing windows are not hidden behind the siding, Retrofit windows are by far the easiest to install. Basically, you remove your existing window and slide in the retrofit window. No framing or adding exterior trim required.
To trim the inside of the window, you fill the gap between the new window and the existing window sills and jambs with the insulation of your choice and use the matching vinyl trim strips to close that small gap. They are peel-n-stick and really couldn't be easier. You can further seal the trim with a bead of caulk.
Well, here is that post from July. It is a bit out of context, because it is a reply to a different post. But it has pictures of the install process that I thought would be helpful. The pictures show installing retrofit windows to aluminum siding. The windows install easier to hardboard style siding panels.
Greg's advice to resize window openings to fit "in stock" windows will save some money on the windows. Sometimes this will be the best option. But if the framing around the window is sound, remodel / retrofit windows will be a fraction of the work to install. Below are some pictures of a remodel window installation. You can see it is very simple to do.
As to whether to get single/double hung or XO type sliders, that may depend on your window sizes also. If these are huge windows, you may need a window design that is half fixed and half single hung, due to the size and shape of the window. These windows go way up in price. Standard single hung is a little more expensive than a slider. But when you put the extra frame piece in the middle and the fixed glass, they go up a lot. Also, if this is an older home with short windows, they may not offer a single hung window for that size. I think the minimum height is 24". In the same regard, if the window is very narrow and tall, they would not offer a slider. Depending on width to length ratio, sliders or single hungs can bind up and be a problem to open and close. Both window types have minimum height and width restrictions. Then if you must have a couple of sliders on a side of a home, do you want to mix in single / double hungs in with them, or vice versa?
Personally, I prefer the remodel windows. They come with the trim built in to the window itself. Being made of heavy vinyl, they won't crack, warp or ever need paint. Also because the material is vinyl, the windows seal up to the house very well, The vinyl frames now come in more colors than white, but all colors are light.
Well, here is a remodel window install. First remove the screws holding in the mobile home window. Measure the opening from side to side and up and down. Subtract 3/8" from the side to side measurement and 1/4" from the up and down measurement. This is your "box order size", or the actual size of the part of the window that slides into the window opening.
Clean off all sealants and if needed, tack down the siding around the window opening.
Install 2 heavy beads (3/8") of window caulking (DAP Dynoflex 230 or similar) around the entire trim flange.
Push window into opening in one smooth move. Have a person hold the window snug to the wall while the other person goes in to adjust and fasten it.
Screws are installed in the sides and sometimes the top and bottom, depending on size and manufacturers instructions. They vary from different manufacturers.
And there it is. A crew of two can easily install 8-10 windows a day, even if the are new at it. That does not count interior trim or sill repairs mentioned earlier.
Here is how the windows look on wood siding. The windows on the right were ordered with Milgard's SunCoatMAX for extra protection from the harsh sun coming in those windows. You can see the tint to them. Great stuff. Keeps carpet and furniture from fading and has much higher insulating qualities.
I would like to add that if this were new construction or done in conjunction with new siding, I would opt for new construction style windows. They also make new construction with a built-in heavy duty J-channel specifically for lap siding, like vinyl siding. But other than that, I like the remodel windows for their performance and ease of installation.