It might be a good idea to get a mobile service engineer to come out and check, adjust/repair and lubricate your brakes for you, just to be on the safe side.

I don't think there's anything desperately difficult about servicing them yourself, particularly if you have the hubs with a re-usable hub nut, but most owners seem to prefer to leave brakes and gas to the experts.

I've yet to dabble with caravan brakes, but I did notice that when I engage the handbrake, the brakes don't lock with the handle vertical until the van has rolled a short distance backward. This is exactly as it should be but it's a bit disconcerting the first time it happens and makes positioning the van on levelling ramps a bit of a challenge.

The answer is to put chocks under the wheels to stop it rolling off.

EDIT: I've attached the AlKo data sheet on overrun brakes for your information.