Are you just looking to retube? JJs are a great way to go; I just retubed mine about a month ago with them and it was NIGHT AND DAY difference.
If the tubes are a bit old, I'd go ahead and change them.
Eurotubes - bob is a great guy to work with
retubing the pball is easy. take off the back, pull out the old and in with the new. make sure they are secure!! If you can have the bias checked it would vastly help the integrity of the amp and its tone.