rotten window sills

The wooden window sills are completely rotten on my home and I would like to install replacement windows. All of the windows I have seen do not address the sills. To remove the sills it looks like I have to remove the old windows, all associated framing, and all of the trim around the window. Is there not a manufacturer that incorporates a new sill in their replacement windows? Thanks in advance for any advice.

Blue

that's because the sills are not p[art of the actual replacement window. The sills can be replaced seperately, btw.

This situation is handled in several ways, depending on who makes the call. We do many full replacements where the complete unit is changed. On some occassions we repair the sills and then install insert windows. On other occassions we install full fiberglass replacements then trim the exterior with low maintenance brick mould trim and sill. There are vinyl products like Kolbe which can install a brick mould and sill at the factory that is used as a full replacement unit. As you can see there are many options depending on the situation.