I agree that it is best to turn the amp over, remove the bottom cover and make your own list, consulting the schematic but checking your amp by visual inspection. This is pretty much true of all amps, especially sansui but especially the tube amps where you may want to not only note down capacitance and voltage but also physical shape and dimensions. For example, in some places it might be nice or convenient to use axial caps, instead of radial, and only a certain maximum length or width will fit nicely....
if you want to start small, identify the coupling caps in the output stage and replace those 4 caps with some nice polypro film caps. No need to go fancy brands, just stick with trusted/reputable brands and appropriate specs (same capacitance (unless you can analyse circuits), but a little higher voltage is ok). In case you are uncertain, the coupling caps I refer to are the "0.3" caps, four of them, near the last tubes in the circuit (i.e. close to the speaker output transformers). Sorry, if this is too elementary for you, just not sure which level we are aiming at here. Assuming the amp works properly in all functions these are the 4 most important caps to replace, as if they go bad they can turn you output tubes on full throttle and toast your output transformers (and these transformers are pretty much the only irreplaceable part on these amps).