Claire, I assume that you plan to do more then remove the belly band. I am guessing that you plan to fill the seam between the top and bottom half's of your 4500. Do you have a leak that you are fixing?
I have done this job twice now:
My First Belly Band Thread
My Second Belly Band Thread
While it is time consuming, and kinda itchy. It is not too difficult. A bunny suit, and a steady hand with a grinder is all that is required. I would love to help, but we are a thousand km, and one WAY expensive ferry, apart.
This coming summer I plan to do another one. As well as finish the two I already done, (sand, bondo, sand, paint). Would it help if I posted videos of the process?
Judging by the fact that you door window opens, I am assuming that you have a 1978 Trillium
4500. Exactly like the one in My Second Belly Band Thread.