Absolutely, and I'm still to earn my badge (under the hood) but building up to it. If a CR2032 fits in your clip, chuck one in, they are common as muck, they sell them in the supermarket these days. If you change the battery while it's powered up you shouldn't loose your programs (is my understanding MJMP correct me if I'm wrong) but based on previous posts where the patches hold whiled powered on with dead battery until power off.... But write them down/save them just in case.
Well if the GTs are old it's worth replacing them. The Mullard long plates will make it sing IMO. And although I've not tried them in an MP1 (SC and others have and liked them
) (I will soon though, I'll put a couple in MikeBs MP1 and compare (he has a Boogie STR in V1 and Mullard Short Plate in V2 currently)). I wouldn't use anything else in my MP2s' now I've discovered them (well SC has got me a little bit interested in the TADs as they are very close to original tubes, though I think the Mullard Long plates are definitely better for how I play these days). I just love the articulation and 3D ness, they track my playing (left and right hand) so well.
IIRC one of Mikes first comments re the Mullard short plate was how it showed up his mistakes (sorry Mike, not having a go BTW), which I understood because they are sooo articulate, but he's tightened up his playing but also started to expand into what they let you do.