When I refurbed both my Princetons I installed a bias adjust pot so I could dial it in with my DVOM. If you go to Antique electronic supply...
http://www.tubesandmore.com/
They sell direct replacement cap cans also replace the electrloytic caps in addition to what 6S9L stated. These are sweet and not to mention valuable amps these days. Is your amp a Silver face with or without the drip edge moulding around the grill cloth?
Heres my little collection one is a 64 6G2 Princeton and the other is a 69 blackline Dripedge PR. BTW they are beautiful in stereo!!
Edited for safety warning . If you decide to do the work yourself get the right tools and EDUCATE yourself. While some find it easy and fun to refurb these old beauties as I do. You can sho-enuff FRY/KILL YOUR KEISTER!! It isnt hard nor is it rocket science but you are dealing will high voltages! Make sure you know what your going to do before you get into it, lest yee wake up on the floor in a puddle of thy own pee!
Feel free to PM me for any advice Ill be happy to help you along.
Git-tires EC Custom Strat, Gibson ES-335, Custom built Tele, Fender Highway 1 P-Bass, Martin 000-28EC Acoustic, Gibson SG Classic
Hearin aids-AmphsCustom hand built 5E3 Magic Markie Mojotone Amph, Fender Blackline dripedge 69 Princeton Reverb, 69 SF/DE Vibro-Champ, 64 Blackface Deluxe reverb, 64 Princeton 6G2 Fender, D'Lite ODS 22, Rumble 60 Bass amph
EffectsBoss CH1 Chorus, Boss DD-3 Delay, Vox wah, Tonebone Classic, TS-9 modded, Bad Bob,Sweetsound Mojo-vibe, Boss RC-20XL Loopstation, Peterson Strobstomp, ZYS pedal, Keeley Comp, Boss LS-2, Zendrive, Menatone Howie