I’m looking to replace an uncomfortable west-facing picture window which is right where we like to sit, with a high performance unit (i.e. U=0.14, SGHC=0.2), and my main concern is getting a proper install.  This isn’t something I think I should tackle myself but I’m also not aware of high-performance builders in the area.  So specific questions I have are:
(1) Am I worried about nothing and most installers could do a good job?
(2) Or, any tips on finding a good installer?
(3) Are some units easier to install OR more forgiving of imperfect installs?  For instance, I have a quote for a thick IGU from LiteZone that could have a frameless install (they recommend this).  Would that be any easier to install/more forgiving than a window with a frame?  Or would it be harder/less forgiving?  Or is there no real difference? 
(4) Any windows I should be looking at outside of LiteZone or Alpen?  I’m assuming overseas brands are a poor choice due to the shipping for just one unit.

I am in the Harrisonburg, Virginia area if that helps.