Pretty postive I know what is causing the noise with your front door.  My
Carat was wind noise free until just a few months ago.  Then the weather
stripping that the front window goes up into started to come apart.  It took
awhile but the center of that rubber window track that the window slides into
and seals in came apart from the rest of the rubber and I ripped it out (it is
just a little thin strip of felt stuff).  But since then I have had similar
wind noise.  I figure your PO had this same thing happen to him.  Solution:
get new rubber seal around your window (at least the upper part anyway).  Your
local dealer sells them, and so does West Coast Metric (I think) but check the
dealer first 'cause sometimes they are cheaper than WCM (they buy some of
thier stuff from the dealer and then mark it up!)
As to your sliding door problem, maybe try ome chalky powder on the door jamb,
and then shutting the door, then reopen.  Where ever it isn't white on the
black seal is where it is leaking or not sealing properly.
Hope this helps,
Ken Wilford
Van-Again
John 3:16