: The shop who arranged the repair did not seem to know much about
: these watches at all. I asked about water resistance, and they
: said best to treat it as 30m, but I have seen other info on the
: web mentioning 100m. Having been factory serviced I would expect
: it to be at the original water resistance, do you know what that
: would be?

Some late Autavias, such as the aptly named Diver 100 below, made a virtue of increased water resistance but the majority of the models were indeed only water resistant to 30m:

Additionally, I personally believe it's worthwhile treating even a freshly serviced vintage watch as if it has pretty minimal WR. OK for a splash of rain but I wouldn't take it in the shower. Some people do but I take a better safe than sorry line - the service may have replaced gaskets, but will it have done anything about decades of metal on metal contact reducing tolerances? Probably not. A healthy sense of minor paranoia about it might save some expense down the line!

: Also the crown only winds in one direction, and I don't feel any
: mechanical resistance when doing that, so I'm not sure if the
: crown winds the watch or if it is only the auto-winder that does
: it.

Yes, you can manually wind the watch - anyone with a few watches in a collection is probably used to giving their automatics a bit of help when putting them on with a few turns of manual winding. Being right-handed, I like to turn the watch so it's facing me and wind the crown away from me.

: Lastly, the shop set the date wrong - is it ok/possible to wind
: back to an earlier date?

Older movements rarely have a 'hackable' date mechanism - you'll have noticed the crown only has in or out positions, nothing for quick-setting the date. The date change is uni-directional too - winding backwards for any length of time isn't advisable for the mechanism and doing so won't set the date backwards anyway. Some people wind back and forward around the time the date changes to sort of 'fast-forward' the date but the ideal way is to wind the hands around forward the correct number of times for the date you want. Given that that's pretty onerous, many people with larger collections just resign themselves to the fact that their watch is unlikely to be showing the correct date and get that information from PCs, smartphones etc - might sound troublesome, but you soon get used to not being able to trust the date your watch is showing :)

I might make it sound like you need to treat the watch with kid gloves - you don't, but handling a 40 year old mechanical device with due care is often to the benefit of both its longevity and your bank balance, so well worth doing!