Hi Ron, While your truck is really not that old in years, you have a
120K on it, so it's seen some use.
Yes, I'd recommend changing them, but not for $300. If you cannot change them yourself, maybe find a friend who will do the job for you, and "grease" him (pay him) rather than your local dealer.
While you're doing them, also change all the heater hoses too, and buy fresh proper coolant.
All your Hose Clamps should be fine, and you probably can re-use them, provided they'll come off without destroying them.
The Bottom Hose Clamps are usually buried on a chevy truck, and mucho trouble, and cuss words to get them off. One needs to be a surgeon to get them. My '97 Tahoe was like this.
The Heater Hoses are no special deal, any auto-zone, pep boys will have what you need. Just remove one section at a time, copy the length with the new heater hose, and install, then go onto the next section till they're all replaced with new.
When I did my Tahoe a couple years ago, I got tired of seeing crusty, dried out Dexcool Coolant accumilating where the quick connect fitting for the heater hose is on the Intake Manifold.
I bought a standard 3/4" straight heater hose intake fitting, installed it with a bit of teflon pipe dope, threw the quick connect fitting, and hoses in the garbage, and never looked back. Been fine ever since with no leakage.
The thing with hoses, is they might look perfectly fine. Problem is, you never know at this point in time with the mileage you have when they'll fail.
Better to get them now, and better to be safe than sorry, than get caught somewhere in the middle of nowhere with a breakdown. Mark