Hi, nice CC, and in black too! Mine is a black '91 as well, and I've had it from new. Never really had to consider whether / how to fully restore it as give or take the odd month here and there, it's been in regular service for almost 20 years now, initially as my only MTB, and then as a roadie / second bike.
Basically I took the 'keep it as original as possible, but not to the detriment of the ride / ownership experience etc' view, so in other words it's had bits improved / replaced as I've gone along, but I'm no rivet counter, so originality hasn't been the over-riding priority. In no particular order:
New wheelset to replace wonky Ukai's (Campag Mirox/LX hubs)
Lightweight seatpost
Charge Spoon (Avocet was torn and had gone really hard... :shock:
Deore V' brakes and levers
Deore DX thumbies (sold all the XC Ltd stuff on fleabay)
Had the crusty old P2's powder coated and re-decaled
Replaced the knackered / bent Suntour RD with an LX
New SRAM chain
Original (heavy I know) BB & chainset/cranks still going strong (over 20,000 miles and counting)
Syncros stem
Kona Jackshit grips
Have decided to keep the frame as is, warts and all, partly as many of the scars tell a story, and partly because I've been fairly successful to date rubbing back/priming/spraying the worst areas of cable rub, so will probably do the same with the other blemishes - that way I retain the '91 patina of slightly faded paint and chipped decals etc.
Couple of pics of P2's before & after and some of the other mods.
So, I suppose what I'm saying is, do what you think is best subject to your intended use - you're the one with the personal connection to the bike, after all. If it were me, I'd do a rolling resto of necessary parts and retain as much of the patina as possible!
Whatever you decide, hope you enjoy the next few years with the bike as much as I have - they don't make Konas like they used to you know