First of all, are you sure it is the crankcase cover seal that's failed? It is worth wiping clean everything on the right hand side and checking all the other possible (slightly easier to deal with) culprits first.

To remove the cover, you'll need to remove the water pump, oil banjos, clutch cable, the footrest (maybe the brake pedal too) and detach the rear master cylinder. You do not need to remove the circular clutch cover. When you loosen the bolts, unscrew diagonally opposite ones a little at a time. Also watch out for the two dowels as they may well drop out and are easy to lose. You shouldn't need too much brute force, a mallet shouldn't really be necessary, and if so only a light tap will be required to unseat the gasket.

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