[StarGate]

Sounds like you intend to do most maintenance yourself so first line of business would be to acquire a good service manual for your bike. You can probably find a clymers on ebay or a local or Internet cycle supply business.
There are a few threads on the forums debating what oil to use but bottom line is it's your choice. Majority here seem to prefer a good synthetic or 10w 40 oil that has no additives. IE. Castrol GTX 10w 40 or if you operate in a hotter climate go to a 20w 50 for summer operations. I don't have a liquid cooled bike but have seen on here where a 60% water 40% coolant was recommended.

For checking other things I would suggest using the mileage on the bike and do scheduled maintenance. Check things like valve lash based on that unless you have symptoms that indicate earlier service/repair is needed. It sounds like you need to get a meter and track down the problem with your horns and you will have a schematic to aid in that with a service manual.