There are some goods books on eBay and Amazon.
Buy a few simple tools and do it yourself.
The basics are simple
Fuel filter
Plugs
Oil filter if it has one.
Gear box oil
Check fuel pipes and connection replace if needled.
Grease battery terminals check if they are tight.
Grease everything that moves.
Tricky stuff
Impella only needs doing every couple of years, some people only change if poor Tell tail.
Carb clean - but this only ever done if there are issues and would cost more on top of a service.
I'm not a gynachologist but I'll have a good look.