Welcome. If you peruse the forum search, you should find a thread or two about the 38 Ocean or the similar 40 Ocean (2 years later model). Like
this one.
There's also a long thread where owners
report common issues with their models here.
As for your questions, the hot water tank is, uhm, maybe 40 - 60 litre? I've not really measured it. As you'll have probably have the MD22 engine it will be full of 90°C hot water after running the engine for a while, which means mixed down with cold water to non-scalding temperatures it will last quite a while! We usually get at least four showers out of it. We had to fit a thermostatic mixing valve on ours as it was too hot for the plastic pipes (bit of an oversight by Bavaria then).
Sockets are easy to retrofit as access to places is surprisingly good by comparison to other boats! We've got them in every cabin, although it was already done that way when we got the boat.
Our sprayhood on top of the glass windscreen requires undoing two straps and then opening two zips on the sides partially - takes about one minute to drop, not that we do this often - the center glass window is openable after all.
I don't know what you mean by a gypsy on the mast. Our gypsy is on the windlass?
If you've not found a boat yet, our 40 Ocean is coming up for sale this winter in Spain