I know it has been suggested that you back into the larger stuff, but be advised that it is a lot easier to bend the parts of your mower that are attached to the 3pt hitch, or the lower lift arms themselves when backing into stuff. I learned the hard way, and now only bush hog stuff that I can drive the tractor over. However, I do drive over some pretty big stuff, which isn't good for the tractor, either. I always figured if the tractor won't run over it, the bush hog probably shouldn't either. A good bumper with a grill guard is a must if your not lucky enough to have a front end loader (FEL).
M10 is simply a metric bolt and any bolt/fastener store will probably carry it. I generally carry about half a dozen shear bolts in my toolbox along with two nuts for each one, for locking them on. The two wrenches were suggested, but how about a hammer and punch, in case you have to punch out the broken piece? The new bolt usually works, but sometimes the sheared piece can use a little persuasion.
Did anyone mention taking the two halves of the bush hog pto shaft apart and greasing them so they will slide easier? If so, I missed it, but thought it was worth mentioning. The grease fittings at each end are for the u-joints, not the slip part of that shaft.
David from jax