#1
I have a little Kustom amp, Kustom tube 12, thaqt I bought for 80 dollars about a year ago. I've read some reviews on it and there are some where they say that they changed the tubes on it and it sounded a lot better.
I'm pretty sure it's only a hybrid in the clean channel, on the gain channel it's just a solid state.. and I have a DS-1 to cover the distortion I want.

Since I'm getting a few bucks tomorrow, probably somewhere around 40, I was wondering if it would really make that much of a difference in changing the tubes since it's not a full tube amp.
Oh, and it's a 12ax7 tube, if that matters at all
#2
Go for it.
Since tubes are cheap, even if it makes a minuscule difference, it's only 10 bucks.
Call me Wes.
Gear:
Fender American Deluxe HSS Strat
Chicago Blues Box Roadhouse
Bad Cat Cougar 5
1957 Gibson GA-5
Ceriatone 18w TMB Combo
Hughes & Kettner Tube Factor
Various Ibanez TS9s
Weber MASS Attenuator