sliding door replacement?

heres the problem- I bought a pontiac transport 1994 for a good price because it was stolen/recoverd,some minor front door panel damage,etc.also the SLIDING door was off- yes off and inside the van.
I thought how hard can this be just to put the door back on?lol
When we attempted to put the door back on the upper sliding arm broke off the top of the door where it bolts on! the top of the door is fiberglass.Got a chiltins and it says to unbolt arms off the door and install on van,then while holding weight of the door to bolt on.
o.k. got it- now how do I get the upper arm bracket back on the top of the door when there is a gaping hole where the fiberglass broke.The bottom of the door and traching seems fine so I would hate to have to buy another door- does anyone think J.B. weld or a fiber resin glue would work? has anyoen ever replaced one of these doors?please respond if oyu have any thoughts.Thank You,Lisa

In as much as repair is considered. maybe something in these 2 pages could help:
www.avigex.ca/xport/repair1.jpg
www.avigex.ca/xport/repair2.jpg