The change out caps comment----
That is a whole can of opinions of which there are many
Not all caps are failing, not all boards have cold solder joints, not all units have corrosive glue damage. So, as the saying goes, 'what you gonna do?'
All the switches need to be cleaned. To get to those switches and do it right you will have to get into major board teardown. If you have the board torn down well lookie there the caps are right where you can get at them. I for one find getting at those boards as time consuming as replacing caps and reflowing solder points. You could just change out the known suspects, Sanyo sky blue low value electrolytics and tantalums which are usually in the audio path but why when for just a few $$ more and a short amount of time you could change the others as well And that power supply, 40 years of slow toasting away, why not do a little preventive work here as well and upgrade those toasty critters to 105c rated panasonics. Gives you a chance to check supply voltage too. Oh, and while you are in there cleaning and such its a good time to replace the pesky vd1212 double diodes.
Now you have everything apart lets also look at the service manual and get after all those fuse-able resistors, oh and re-greasing the outputs is a good idea too. The finicky offset and bias trimmers could use a upgrade to multi turn potentiometers as well
As you now see its not just cap slinging but more a matter of opportunity. If the piece is one you find will never leave your stable of gear then my thought is do it once, do it right, then put it in the rack and enjoy for years to come
Short version of the above --- if the unit is all apart do everything once and be done for good.
Your gear will thank you for it.
-Lee