I'm getting a doorwall installed from Home Depot. Standard Instalation plus putting up caseings on the interior,if they are provided are included. However, the Vinyl/Aluminum trim on the exterior is not included. The contracter wants b/n $75-100 to install it. That seems a bit steep! Do you think I should just buy the materials and put it up myself? How difficult is it? Anyone have a guide? How expensive would the whole project be? How much time? All input is welcome. Thanx!!!!