In terms of reference, I'd recommend this book:
Kit Airplane Construction
https://www.eaa.org/shop/product-detail ... pr=2658244
I'm sure it's available from Amazon and other places too.
The Rotax 912 series engines are very popular these days. The operators manual and maintenance manuals are available to download here https://www.rotax-owner.com/en/support- ... es-engines
In terms of specific maintenance manuals for aircraft types, they are a little more difficult to come across. If you're interested in building an aircraft, I'd recommend you get in touch with one of the associations like the NMAI. They can put you in touch with members who are currently building their own aircraft. I know last week four ICP Savannah / Ventura kits were delivered to Limetree Airfield so that may be a good place to start. They also have finished examples of the aircraft there for you to take a look at.