Joss, Not enough info for any kind of estimate. The job in itself is not a big one. If the new door height is not greater than the existing window height, it will just require framing in the new opening and matching your inside and outside trim. 2-3 day job with 2 people. If the interior and exterior are FANCY...a little bit longer

Thank you. The height of the window is approximately 6'-9" and I'm assuming the same height the door would have to be. I've heard somewhere that 6'-8" is an average door height, but I'm not sure if that would be the same for a doorway leading to the outside. However, the window is longer than the door and most likely the wall would have to be cut into on the right side of the window. The room that the door is going in has a rather low 8' height ceiling. I'm only looking for an approximate cost. Are we talking thousands or hundreds? Thanks for any info. Joss

Joss, The box your doors came in should tell you the height.The standard is usually 6/8. The fact that the window height will allow for the installation without changing the header is a big plus. It sounds like the framing is only going to effect 1 side wall. $600-750 would be a fair estimate unless your labor rates are much higher than other areas. I live in MASS and recently saw a sign at the local Home Depot ~Patio Doors Installed $450 and up~

To reframe the opening, weatherproof the exterior, sheetrock, compound and install all moldings in the interior wouldn't get done by any professional for under $2000. plus the cost of the door.
Ron