Good deal you got. I bought mine a few months ago and also got the MMM, I think it was $23k for mine....you got a good deal.
I would say yes buy or build yourself some under armor (not the clothes) for your machine. You look at that fan under there and think how in the heck can anything get up in there...but trust me it does. I have not lost the fan yet, but the rubber bootie has been damaged. I would also look hard at the BXpanded piranha tooth bar (PTB) and/or a Ratchet Rake, they are two very different tooth bars, and they will bring a TON of more usefulness to your new machine. I think that they are a must, and are good at two very different types of jobs.
I would also say unless you are using diesel fuel pretty quickly stay away from bio diesel. If that stuff is left in the tank it will start to grow. Most people do not use fuel that quickly on the little BX, it is pretty thrifty on the fuel. I have not had that happen myself, but enough people have told me this that I do think it is fact.
Only other thing I would say is if you plan on working after dark get yourself some other lights, the lights on the front of the tractor are quite good, but with the loader on they get blocked quite a bit.
I have been very happy with the little machine, you will be shocked at what it will pickup and move. I don't think it is the best mower, but I don't think you got a deck. Let the air out of the tires and it mows much less bouncy. I have a bad back and a bumpy yard. Keep us updated, I think you will love the machine and be shocked at how little fuel it uses to get the job done.