That all sounds pretty good for something that's been in the loft for so long.
Among the know issues, 2 of them relate to the HT line. Firstly, there are a number of resistors of the old composite type and these tend to have gone to high value. These include the ones intended to blead the high voltage electrolytics on the HT line, so making them safe after switch off. Secondly, many people do decide to change those caps; doing both the caps and the resistors at the same time make sense.
Take a look at this
https://www.vintage-radio.net/forum/...=Kenwood+TS520 and the follow up thread. All of the Kenwood/trio hybrids share many common features.
As yet, I've done nothing to my 530, other than fit an additional antenna input socket to allow the use of separate transmit and receive antennas at the same time (inverted V and magloop respectively).
B