uh o
thats a big job! basicaly, everything needs to come out and be put back in the new cases .
look at jim snells Gas Gas engine repair videos on youtube.
yes you sometimes need to heat up the cases to get bearings out etc etc
when installing the bearings back in the new cases put the bearing in a freezer/fridge and heat up the area its going in to.
it makes it alot easier trying to get it back in.
good luck,
ben