#1
I have no experience replacing tubes, but could I do it myself?
Gear:
Gibson Vintage Mahogany LP
Line 6 Echo Park
Peavey Classic 30
Seagull Entourage Mini Jumbo
Vox V847A Wahwah pedal
#2
I just done it myself and the answer is yes, however if you want to change the bias its an entirely different story
Ibanez PGM301 signed by Paul Gilbert
Ibanez PGM 500
Ibanez Fireman custom
Saving for a GH100L/VH100R
Orange PPC212 2X12
#3
I'm assuming you want to change the tubes in your C30?

Changing tubes is easy. You just pull them out and put the new ones in. You may need to adjust the bias though - I'm not sure if the C30 is fixed or adjustable bias. If its fixed then you have nothing to worry about, just change the tubes and you're done. However, if its adjustable then you will need to rebias the amp after you change the tubes.
#4
1. Turn off all power, remove power leads
2.Make sure tubes are cool
3.Pull them out (They come out very easily)
4.with some Electrical contact cleaner, clean the sockets by spraying it on the old tubes and just putting them in and out of the socket
5.Place new tubes in
6.Re plug all power/speaker cables
7.Leave amp to warm up for 5 mins
8.enjoy

As far as biasing goes it's a lot more confusing
Ibanez PGM301 signed by Paul Gilbert
Ibanez PGM 500
Ibanez Fireman custom
Saving for a GH100L/VH100R
Orange PPC212 2X12