bearing
I agree with the comments about the bearing having to be installed correctley, be carefull to heat the hub evenly and it would help to chiil the bearing as well, google bmw spesial tool 36.3.650, the key to correct bearing installation is to get the preload correct.
the same commonsense approach applies to the head races, in short if you have the correct tools - use the internet or clymer manual for refference- and take your time - it is comparatively straight forward.
however, I can not find any specifacation for highload capabilty bearings in the bikes specs. like all things you get what you pay for but all reputable bearing manufactureres e.g FAG, SKF etc are made to a common manufacturing specifacation and should be ok if you stick to the bearing number that is on the bearing that is fitted (ignore BMW part numbers) if it has rubber seal then fit a bearing with rubber seals - unless you feel metal seals are more suitable and do not use C3 clearence bearings unless they are called for in the bike specs.