Actually I do have an SMT Walkman Professional already that I serviced myself.
I enjoy its unique sound and find it sounds better stock with chrome/metal tape than my other mp3 players. And it has a rather powerful amp that can drive headphones better than most if not all new mp3 players. And you are right, it's rather large. However, there are similar playback-only models like the DC2 and DD9 that are smaller.
I do collect walkmans, and know about the sungei road market and have actually obtained a few units from there, but none of them are the higher end models I'm seeking for.
DD units mostly do not have belts (but the professional and dd9 does for reel takeup).
Thankfully belts are mostly easy to replace, but as you said, miniature components like capacitors that need replacing are difficult to replace, but doable.