I too did the 6 speed upgrade myself to my 93.
Nice upgrade.
Advantages are the same as having the 6 speed in the newer NSX's, and frankly I would think a 6spd 92 would be worth thousands more than a 5 spd 92.
All and all, if you shop, bargan and trade, (and sell your old 5 speed if it's not worn out) it's not that expensive.
Well worth it for many reasons, but like all subjects on Prime, open to opinion.
david