Replacing the clutch discs is more of a sloppy job than anything. Be sure to wear gloves and have a drip pan ready and a roll of paper towels.
You will need a case gasket for sure. The hardest part is cleaning. While your in there clean the oil uptake screen.
Here is a pic of the assembly (less oil and grime)
Unloosen the clutch plate bolts evenly. There will be no tension on the springs once they are loose. Once the bolts are removed, remove the whole clutch/disc package. Mark or seperate the clutch plate that is against the blutch basket (first steel disc in..last out) This disc is slightly thicker than the rest.
Clean each steel disc plate with Westleys White Wall Cleaner, or Chome Wheel Cleaner......or solvent.
On a flat surface, sand each disc with 320 or 240 grit wet dry sandpaper to renew the surface. Reinstall the package the same way you removed it. Tighten the bolts - don't overtighten- the clutch basket is aluminum.
Put on a new case gasket with a little sealer and reassemble!
I would bet that the clutch discs are good and they only need to be cleaned.
Remember-30wt oil in the crankcase! 9 times out of 10 someone may of put an additive in the engine that caused the clutch problem!
Good luck..ain't no biggie