Hi Margaret,
The biggest difference in handling between the two boats will be down to weight rather than keel configuration so you will need to think ahead a bit more, both for turning and for stopping. The extra displacement also means you should forget anything you've learned about pushimg the boat around by hand - if collision is imminent, the best you can do is to drop a fender in the closing gap rather than any attempt at pushing off.
Undoubtedly a fin and skeg will need a bit more way on astern before responding to the helm than a fin and spade design. To moor stern to in high winds it's worth turning your boat before entering the harbour, then you don't have to change direction when close to other boats. It's the stopped condition when changing between ahead and astern that leaves you most vulnerable to the wind, After one season you should be completely adapted to a boat which will handle differently, but not really more difficult.
A bow thruster will help in cross winds, but it's worth seeing how you get on without for a season before making the spend required for that unless, of course, you buy a boat with one already fitted.
A M376 will be both stable and stiff, under way and at anchor, and is a prime example of Bill Dixon's skill in designing a well balanced rig with a delightfully light helm.
Peter.