To make the doors openable, I cut a section out of the middle of the wall, but keeping a bit at the bottom, and keeping the tabs that fold out (that I glue the strip of metal too) for support. Then I cut the space out of the door frame, and folded it so a door frame half sits on both sides of the wall. Then I cut out the door, and did not glue it together flat - I left it so each half of the door can slide between the halves of the open door fame and the wall - ensuring the hole in the wall was just thin enough that the door can surround it along the edges, stopping the door from flopping around. Anyway, here's a bunch of pics that hopefully explain a bit better.
Also, support beams for the walls. Basically, cut clots into them, so they can sit down over the top of where two walls meet to help hold them in position. I found I had to cut some pretty big slots into the beams, because the laminated walls were a lot thicker than plain paper, and they ended up pretty much being more for decoration - and adding more 3D'ness to the map, than providing any actual support. But I like them :)
And here's the doors.