I have looked into have a pro assemble a tank in-place before, and sadly I never did find one. Its a potential liability nightmare for pros, so they wont do it.
Its not that hard to rebuild yourself and just get a friend to help lift the panels, depending on how large the panels are. Cleaning the glass of previous residue really would be the hardest part, as you need to remove 100% of the old silicon from all edges. After that its just laying bead of silicon on the bottom, and placing one side at a time from there. Square up each side from top to bottom and use a strap or gentle clamp to hold in place. Once that is cured, you can do the inner seal. Hardest part of that is taping off the edges, but takes 10min or less from there.