I see that the Workshop Manual isn't free to download.
So I remembered that I have a Haynes manual that covers triples and fours, '91-'99.
The oil sight glass is circular (checked with bike on center stand or level and upright) on the right hand side of the motor, low, directly below the cylinders, below the side cover, above the pipes.
The oil drain plug is underneath at about the same point as the sight glass front to back. It's probably an Allen headed plug in the sump.
The oil filter is underneath, behind (towards the rear) of the drain plug. You'll see a bolt in the center of a larger finned circular flange. You'll need a filter, small and large rubber o-rings to replace.
Posted with TapaTalk