NV4500 5 speed 3rd gear synchro going out? 1994 K3500 6.5 diesel

It seems the 3rd gear synchro is going out in the 1994 K3500. That is a NV4500, correct?

I've never torn into a transmission or differential before.

The trans is grinding going into 3rd gear. If you don't rev up to normal speeds in 2nd and shift excrutiatingly slowly the grinding can be avoided.

Can anybody give me advice or parts numbers for what will be needed?

How big a job is this? Is this best left to a guy that knows trannys well?

Would I be money ahead to look for a good used NV4500 for a diesel?

I thought I read somewhere that these transmissions are diesel specific? Different spline count or something. Can anybody verify.

Any advice would be appreciated.

If there is a better place to post this or a link to a how to, I would much appreciate a heads up.