#1
Ok one of the tubes blew out in my head. never had the change them yet. and I was just wondering if they are easy to change? and if anyone can recommend a certain type of tube or brand etc..
#2
Use the same type of tube that it came with its not good to use a different type
#3
it's safer to replace the tube with one that is simlar to the one you have, e.g you have a sovtec 12ax7 so replace it with something like an electro harmonix 12ax7, whilst some amps can take different tubes overall it's safer to stay with the type of tube you allready have
#4
Same tube type. If you've got 6L6GCs in there, put new 6L6GCs in. if you've got EL34s, put in EL34s, brand doesn't really matter too much. If you need new power tubes (more likely than preamp tubes) then you'll want a matched pair or quad however many power tubes you've got. If you've only got one power tube then you don't need to worry about matching. JJs are the best current production tubes by general consensus, although, I've heard one person say that they're 6V6s are a little to dark for his tastes. If you wanna go NOS it'll cost extra, but some swear by them.

Resource thread should have places to buy new tubes from. You'll also need to adjust the bias, which I DO NOT recommend you doing yourself unless you're familiar with valve amps, and I'd guess that you aren't from the OP. A local amp tech should be able to adjust the bias for you.

You may want to check out the everything you ever wanted to know about tubes thread in GGA to give you some ideas as well.