Clutch or transmissio

I've bought a 2001 XJ600N with 11k. When I went to pick it up, the bike jerked & creeped when I put it in gear. Seller did mention that the clutch cable needed replacing, so after attempting further adjustments he offered to replace it. Unfortunately the new cable didn't sort it. A mechanic-friend of the seller opened the clutch & replaced the collapsed thrust bearing. When I finally got to pick th bike up, I had to adjust the clutch again as the bike jerked & stalled. On the ride home gear changes got harder & harder, but I made it. Now I can't get it out of neutral! Adjusting the cable doesn't make a difference, so it looks like something internal. Before I go spending a fortune & taking it to bits, does anyone have an idea what it might be? Or what I should be looking for? I'm so glad that I got the bike for a bargain price... oh, it needs new downpipes too... & the MOT expires 1st December!