That clunk may simply be a universal joint (albeit the mitsu ones don't go bad very often).

The starting in 2nd is something else altogether.

These tranny's are pretty indestructable but with your mileage it may be time for a rebuild.

Definitely start by trying to do a tranny flush and see if that fixes the problem (this is where they force out the old fluid using new fluid).

In my neck of the woods (Silicon Valley/San Jose CA) it cost about $75 to do at a Speedie Oil and Tune Up. They're a nationwide lube company so you can check locally.

I'm not sure exactly how they hook things up but where I had it done, they knew when to stop by ensuring only clean fluid was coming out versus any old dirty fluid.

You may have to do this a couple of times as the new fluid may loosen deposits which may have been clogging/restricting fluid flow your tranny. Once the fresh tranny fluid detergents eat them away.

Also find out if the tranny filter has been cleaned or replaced ever. I'd suggest at least cleaning it (it's a wire unit that can be cleaned and reused) or replacing it entirely. I understand you will need to remove a cross member to access it.