I lucked out on a good deal for the MJ2 and some tubes, plus I have quite a few from when I owned the Lyr and Lyr 2. I'm in the process of moving now but I should have my hands on the amp in a week or so.
Tube rolling is fun since you have so many ways to tweak the sound based on the tube manufacturer, tube family (6922, 7308, E188CC, etc.), even date of manufacture (NOS vs new). Be care careful though, I can get out of control and ridiculously expensive!
Two things I would recommend: a set of "socket saver" adapters that will raise the tubes high enough to swap easily and two, the patience to let the tubes burn in and open up before trying a different set.
Lastly, you might want to consider some tube dampers to reduce some of the microphonics that tubes can have. PM me and I can provide suggestions for the dampers and socket savers.
All this is IMHO and YMMV! But really, it can be fun and rewarding!
Cheers!
-HK sends