Hi Jay,
I guess you may have sorted your problems by now!
You can buy the genuine merc glass without openers for about £100 each, they have a light green tint, you can get them for both doors and the rear side panels as well.
or if you look on ebay there is a van window specialist based in Castleford (called Van Windows) that does the door windows in dark tint, I think they're about £65 plus postage. They also sell a fitting "kit". To be honest it's not that complicated, you chop the holes in the van using the inner skin as a guide, prep the surfaces carefully (degrease etc) apply the adhesive to van side or glass..... then whack the window on, tape up and stand back to admire the result!!!
Having said that.....there's a lot that [u]could/can/will probably [u] go wrong, levels, correct amount of adhesive (not enough = disaster - leaks etc, too much = looks like you did it wearing boxing gloves lol!)
Actually when I think about it, it's probably best to get somebody experienced to fit them for you.
There are also plastic inner trims available from Merc, however if your handy with the carpet trimming you don't really need them.
Re the seat fixings, I am in a similar position ie I have some traveliner seats but not quite sure how I'm going to mount them, I'm just looking into acquiring the sockkets.
Don't get mixed up with the quick release V class captains seats that do fit onto a set of floor mounted "rails".
If you learn anything useful please let me know!