#1
Ok so I blew one tube in my head and I figured I'll replace all four. Now I'm looking at getting electro-harmonix 6l6eh to replace the ones I have. I would have a problem putting them in? I completely new to the whole tube aspect of amps.
#2
EHX tubes are kinda crappy imo but some people like them. You should just be able to pop em in and go. The + has a bias pot but not sure on test points. I'd go the extra mile and get some decent 6L6s from a reputable online shop, have them match 'em up so they all come to you in a nice tight bias range.

dougstubes.com
tubedepot.com
thetubestore.com
eurotubes.com
hotroxuk.com
#3
just pull the old ones out and put the new ones in
make sure amp is off and disconnected