I would start with two or three concurrent projects. Backup your changes frequently - named MyFile00, MyFile01, etc.
Importing the Excel Spreadsheets would be the quickest start.
I have collected many links over the years, some are in this post. The first five links are a good start
One of my Scoop.it sites is about Filemaker (34 pages - navigate at bottom) http://www.scoop.it/t/filemaker-info/
Links about using templates..... https://www.google.com/search?q=modify+templates+filemaker
Check out my youtube channel for some screencasts about developing in Filemaker.
I would always urge you to start from scratch and build your file properly instead of trying to bend a starter solution to your needs.
But then you do have to understand how to work in Filemaker. Because if you want to develop a database you need a developer. Or you will need to become one yourself.