Don't stop. You'll kick yourself.
To me, you have three options about a ride. First is to fix the 600. That is the worst option, methinks. Parts for those are harder to find than a 06-10 or 11-18 600, so you are limited on sources; therefore, is more expensive to fix.
Second, part the ol' girl out and use the money to "upgrade" to an 06-10, or an L1 and newer. (I know that second generation is not economical upon initial investment) Those first 5 model years and then latter 8 are pretty much lego within the generations once the street fairing is off. I just commented on another thread about a stator cover and if you click the link, you'll see it's the same damned part number across THIRTEEN years of the 600:
I've seen your knowledge over the years, so I am sure that you don't need a lesson on cross-referencing part numbers. The best part about sportbikes in general is that as long as you aren't looking for a front wheel, junk yards are filled to the tits with parts. Thirteen years of interchangeability? You're laughing. Trust me: 13 years of gixxer parts are stupid-easy to find. Trying to find parts for my '14 675R Daytona has illustrated to me just how spoiled I was. When I first prepped the 600, I was buying PAIRS of low-mileage wheels for $400 (rim, discs, bearings, muthafuckin' cush drive/sprocket carrier and all). I had to buy a brand new front wheel plus discs for almost the cost of what you need to pay to fix your machine in total for the Triumph (let's leave exchange rate out of this).
I literally have seven or eight BUCKETS of gixxer spare parts that I had accumulated over just three years and I only ever paid for two of them... for the revered Canadian currency of a cup of Tim Horton's coffee for the pair. Guys were THROWING spares at me.
Third option is to part out the 600 and get an SV or Ninja650. They are cheap as fuck to run. You'll save a bundle on tires, alone. Parts are harder to find than 06-18 600s, but are still cheap AF.
Final point- If you're son is going to trade school, research the FUCK out of grants, bursaries, and scholarships. Go to the trade school he wants to go to and look at every cork board in the place. Go to the department instructors and administrators and ask about any, too. I don't wanna share too many personal details, but I am currently a student, again, at a trade school after an incomplete military career (and after two degrees) and the amount of free money available blows my mind. Long story short- a smart kid doing a good job looking for free money will never spend a dime of his own on his certification.