[popo]

I got home, partially reassembled it enough to turn on. Held the menu button and... the wheel worked! That was likely the "problem". The dealer I bought it from goes through a lot of used kit, so it is natural to assume they know what they're doing. But I guess it worked out better for me. An (apparently) fully working 1D for not a lot! Just need to do a full reassemble of all the bits now and give it a more in depth test to make sure I didn't break something else in taking it apart...