Purchased 3 of the 4 decoders needed to complete to conversion to DCC. Before I left for the railroad show, I tried to get the body shell off one of the B units without success. I took that as an omen that I should hire someone to do the installation. 
Hi Roger, you should be able to pry that off. Just takes a bit of working and should not be a reason to "farm" out the installation. Like Mark says, these are about as easy as it gets.
As he also says, you can program them as the same number or different and then consist them. Personally, I almost always like to use the road number as the decoder address. That way there's never confusion. However, with drawbar attached units (meaning it's a pretty permanent consist) or with numberA and numberB road numbers (and these are normally drawbar units), I make an exception.
Let us know how you got on.