Hi,
it's a very nice and precious watch - I wouldn't recomend to try it yourself!
A simple slip an ruin the hairspring for example (many other channces to ruin something else ...)
and he outcome would be very expensive :-((
If you don't want to "invest " in a factory repair - why not look for a good, competent watchmaker around your place
and have it checked?
A deviation of that amount normally indicates something else (necessary service lubrication ...)
If you'd like to get into working on a watch movement - look for some decent, simple, handwound
time only watch (or even better pocket watch) for your start into "watchmaking" - these can be found
for relatively small money and you can get an idea of the difficulties involved.
Best regards
Suitbert