The information you gave is a bit vague. Is it grinding in reverse and hard to shift in other gears? If so, you probably have an issue with either the clutch or it's linkage. I would insure the freepedal is correct (app 1"). Then visually inspect each piece of the linkage. Pay special attention to egging of the linkage rod holes, worn linkage rod ends, worn or missing pivots, bad body mounts (body lifting when clutch is depressed), and loose or missing pivot mounting bolts.
the filler hole is a square headed plug about half way up the side of the transmission.