Improving GH &can i add sliding door to existing greenhouse?

I have a lean-to greenhouse, 10'x20', aluminum frame, glass windows. I'm working on fixing it up, as it's in sad shape. I need to replace the door, and I like the idea of a sliding door. The door that I want to replace is not sliding, and is a normal sized single door. Anyone know how & where to buy one, and how best to add it?

Also, the aluminum is silver and I was thinking I'd prefer black. Can you paint the aluminum black? Is it possible to upgrade the glass? It's single pane, and I was wondering whether argon-filled panes would work. When I was looking at nicer greenhouse kits, I saw that rubber clamps were available to keep the glass panes in place. Anyone now where I might look for some of these things?

Also, is it worth it to try and rehab a greenhouse, or better to just look for a new one? This had been neglected for years when I bought the house.

Thanks!
Ellen

I wouldn't paint,as you'll be fighting to keep it up looking nice,as it would peel from the humidity.
You can always modify for a sliding door,but it would be the same space as the swing door,if your wanting a bigger door,try double doors or a french type so doors can open,and have them swing out.
I think it's best to go back with a single pane as the frame was designed for,and settle for a solar cover in the winter and shade cloth for the summer.

check craigs list, free cyle and the habitat for humanity re-store stores for your doors cheap is good but free is better...lol.