Mine had been glued shut with body sealer, then pried open and the liner pulled out from the bottom (and bent all to hell) when I got it -- the roof was held in with tape (yuck, some of it is still there!) and with red shop rags stuffed in the sides.
Both lifting angles were broken, and some bits were missing, so I know exactly what you have. Hard to tell just what is going on.
Make sure you get all the bits out from the rails -- I found a chunk under one side that could have screwed me up.
I need to finish my repair -- the roof panel requires to be painted at the edges, and the front slides were missing (!) -- I've not gotten the little pads installed yet. It does open and close, however, and does not whistle or leak.
I presume you do not want to purchase the special tensioning tool to pull the roof panel up tight, so I suggest you simply move the translation bridge back a few millimeters and hold the roof panel forward by hand when installing. It is important that it fit tightly at the front, or it will drag too much on the back edge. Don't forget to remove the alignment pins if you have them before you move the translation bridge back!
I suggest also that you leave the panel just slightly under flush at the front and just slightly over flush at the rear -- this seems to give the least wind noise.
1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!