Should I only repair my blown overhead gasket on a 2002 Honda 900rr Fireblade?

Recently, I bought a 900rr from craiglist. I bought it knowing it had a blown overhead gasket (because the seller reached out to his mechanic last minute) and because of this new problem, I haggled down the price.
After buying the bike I took it to my mechanic for a full inspection on the engine just to be sure about the problem.
Later, the mechanic reveals a whopping 2500k service quote charge. 300 for the gasket system replacement (as I expected), 600 for a new radiator (coolant and water slightly mixed together) and they want to replace the engine.
Honestly, the engine runs great, I've gone 100 with the bike just to see how it fairs with the blown gasket and there is no compression loss.
My question is, I know a blown gasket can be caused by another problem. I don't want to get a new one only for it to be blown again.
Should I just get a new gasket system, or should I replace the radiator as well.
I'm no gearhead, but my thoughts are, if I fix the gasket, I can then just flush the radiator clean and put new antifreeze in it?
Should I just go ahead with the solo overhead gasket fix and not worry about the rest?
Added (1). Update: Forgot to mention the bike runs about anywhere from 200 to 280 degrees Fahrenheit after about 20 minutes of riding! So a blown head gasket seems very likely

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