[font=trebuchet ms]Tubes only 'age' when the're being used. The power supply filter caps may be close to failure, but if there's no pop, crackle, or excessive hum, don't worry about it. And those speakers look like they have Alnico magnets, which are primo units in a lot of people's opinion. Why do you think Celestions are going to be any better? Close your eyes and play. If it sounds good, just kick back and enjoy!
I think you've got what may be a real tone-monster, and it puzzles me (I'm trying to be polite here) that you're prepared to rip it apart before you even know what you have! Peavey used to make some very good amps. I'm not familiar with that particular model, but it looks to me like it may be a winner, just the way it is. Like I said, if it ain't broken, don't try to 'fix' it.[/font]