nvg 3550 swap or rebuilt

I have a 2003 rubicon, my 2nd gear has a grinding noise when I down shift, the mecanic stated that its my synchro and that I needed a rebuilt. All this started with me not changing my oil after a few deep water crossing.

My question is should I stick with the nvg 3550 or should I be looking at something else. Mine is a 5 speed, they did 6 speeds for later models rubicon (tj model) will a six speed fit without any modification or should I be looking at a complete different model.  
6"RCD long arm, 35"trxus

The NSG370 isn't worth the additional costs that would be involved. It has a slightly lower first gear, but also a lower overdrive gear.

So, while you might get a slight advantage off the line, you'll be giving some up in fuel economy when in overdrive. The biggest difference that you'd notice by swapping in a NSG370, is that you'd just be shifting more.

The NSG370 is also developing a reputation for not being nearly as strong as the NV3550.

The creation of the NSG370 had more to do with having one transmission that could be used in many applications, as opposed to replacing one transmission with a better one.  

I had the same problem in my wrangler.  I tore it down and rebuilt it myself.  Only got about $200 into it.  Better than spending over $1000 for a new one.  It works great now.  Plus it was good experience.  I would do it again in a heartbeat.  Just make sure you keep all your parts in order.  

Ive change my oil twice now, and now if i drive 15 mi. or so (hi-way)the tranny run normaly after that. So im thinking of changing my oil again hoping for a miracle.  
6"RCD long arm, 35"trxus