Re: the wireless keyboard, I thought I had a battery stuck inside after removing 2 batteries because looking inside it resembles the end of a battery. Only after removing the grey cover in the center did I see that it's just the seat for the batteries.
I have the same problem with my trackpad as Rod does, doesn't work after removing corroded batteries and cleaning. Doesn't appear to be any way to get inside the switch end though that defies logic since they had to install the switch somehow.