As the previous poster says, preparation is everything. Be careful working on the PCB's as the tracks are not particularly robust. Clean, quick, work with a hot iron and careful solder removal with a vacuum tool will get the job done without lifting tracks or pads. I've seen a few cases where people elect to do a mass component replacement, only to end up making a mess. But if you have good reason to do a replacement, it's essential of course. For my TS-830's and a previous TS-530 I routinely replace all the "hard working" (PSU) electrolytic capacitors, and others as required.
Your RL-1 relay solution is a good one but, despite a lot of commentary to the contrary, the originals or direct replacements have been available from a number of Asian suppliers. I bought a couple two years ago from a Hong Kong company. However, your new PCB and relays are certainly (relatively) future proof.
73, and good luck,
Peter.