The box is crunching when going into second, no leaks visible, clutch fluid is fine, other gears it will shift into fine.

I am thinking its maybe a baulk ring or something, what do you think? Its the original box and has done about 108K.

Whats the best option, can I drop it and change this part, while its out is it worth fitting a kit etc?

It had the whole clutch assy done not long ago, so I think it is a box issue.

I'd get a recon or a secondhand box, are you going to do it yourself? Rebuild kits are fine, but you still need special pullers and be able to set end float etc. IMHO The cost of the tools will out weight the cost of a new recon box.