I disagree
If you are going to invest in a new top end, and I assume you are planning on purchasing a pair of new piston kits and getting your cylinders honed at a local machine shop (not a big expense but a very good idea). The deal is by the time you buy pistons, base gaskets, new o-rings for the head (you should do this unless just recently replaced), maybe consider wrist pin bearings as well. You go to all that expense but not split the case when you know you have debris down there (?). Other than about $20 for a new crank seal and a tube of 1211 to seal the case, the rest is just labor and a lot of extra insurance. You could easily have very small debris left behind that could later get sucked up into the top end and have more damage. Not to mention the damage that you could cause to the crank bearings.
Split the case, flush the bearings out with solvent, clean the crank and wash the cases. Pre lube the bearings and seal and re-assemble. If this is new to you then there is a lot more to know about proper case sealing, torque, etc. So don't be afraid to ask and get all the torque values and sequence before starting.
KO