Someone on the Internet had a great way of changing the the 'not available battery' to three AAA batteries. I did it and it has worked great I have two 100s and the one that I have converted is perfect. The other had a battery that is still working (unbelievable). Polaroids, unlike same camera companies (Canon) seemed design cameras that did not suck the life out of batteries.
I couldn't find the site, but I'll try again tomorrow.
I clean the rollers on mine after every pack. I don't know what you mean by upside down. If you are really that worried, I'll email you a photo on mine (just PM me). By the way FP100b is the best B&W Polaroid every made (in my opinion).
and FP100b in pinhole (homemade not an Automatic100;
The Fujifilm packs are slightly tighter so you have to be very careful with the tabs on the first couple of sheets of film.
EDIT: Here is the site just keep continuing through it and you will get to the batteries. There is a lot of other valuable information there too.: