Hi Alan, if you fancy a bit of fun reading, put prop shaft lubrication in the search box. It's a much discussed and occasionally contentious subject. Broadly speaking, slow reving installations often favour grease, fast reving ones sometimes use oil, the idea being that there is less drag on the shaft. There's plenty of people who would disagree with even that. Me?, I also use Teflon grease, it does the job very well.
For the motor, only lubricate very occasionally with oil. Too much or too often can lead to the oil ending up on the brushes, spoiling performance.
As for the rest of the maintainance, most is obvious. Dry out the boat after use, inside as well as out, try to store the model so air can get in. Remove batteries if you are leaving it for any amount of time. Look after electrical connections, they can tarnish and lead to strange or non functionality. Check all wires from time to time, especially if you have any screw connections. If you have any of those little bags of silica gel that you find packed with electrical goods, keep one in the model while it's stored.
Can't think of anything else, but it was a great question, I recon we've all missed doing these things sometimes, and wondered what is wrong when we go for a sail, I certainly have.
Chas