The museum is open sundays between 12.00 and 16.00. Try to call them then. If you need help with german let me know.
I live 60km from Hannover...but in the other direction :-)
I'm not sure they'll let you "move around" like you want. There are ropes and stuff it seems....museums. But they are a small place. Maybe they can be convinced:-)
I doubt about the plan with thin plastic and solvent. Sounds messy.
I have to do some hunting at work. Will get back to you :-)