On Feb 17, 8:31 am, wrote:
Also, I believe they
are the complete assemblies.

That being the case, try to determine the manufacturer and ask their
customer service for the installation guide/directions. Likewise,
check out window assemblies at Pella. Andersen, showrooms and displays
at the box stores. You could score a match that way and get some
literature that would help. If your windows were flange-nailed types,
you may have to remove inside trim and fill open cavities with
insulation and/or latex foam. In the worst case, exterior trim and
even siding may have to be removed to install proper flashing. It will
be a learning process, but most commercial windows these days are well
refined products so your odds for success are good. HTH

Joe