Rather than just change all capacitors on mass it's a good idea to change one at a time lest you introduce a fault. If you change the lot in one go it's could be difficult to then go back and find a fault as you have made numerous changes instead of one change.. With an amp of this age the only caps that will probably need replacing are the electrolytics - the big round ones, and the coupling capacitors. These last are important because if they're leaky, electrically speaking that is, they could put a positive voltage on valve grids, this means that damage could result.
Before powering it up for the first time it would be good idea to build yourself a simple lamp limiter, there is plenty of info on this forum if you put "lamp limiter" in the search box. Plans and instructions to make one here -
http://www.vintage-radio.com/projects/lamp-limiter.html & here - file:///tmp/mozilla_andy0/Instructable%20-%20Assembling%20a%20series%20lamp%20limiter.pdf A lamp limiter will indicate if you have a fault and will prevent damage to the amp.
If you take it slowly and carefully and check the circuit beforehand it should save trouble later. Andy,.