as far as removing the fan, its hot-glued in.. just heat the hot glue with an old soldering iron,or the tip of your glue gun, and it should come loose.
as far as the memory, you can use pretty much any 30 pin SIMMs. just configure the jumpers accordingly. I put 4 4meg simms in mine, and configured it for 8-megs.. (I know it wastes 8 megs, but i couldnt find any 2meg simms)..
As far as cards to use with the xt-sidecar, your gonna want to stick with old 8-bit ISA cards.. those are pretty hard to find nowadayze.. But, other than that, as long as they fit, and youve got the PC software for them, they should work just like they would in an old XT...