Is there anything I can do before my coaching course to prepare for it?

Read a book on squash, watch good squash, learn the rules and practise your refereeing at team matches. 

Try to get the opportunity to help out at a club night or junior coaching sessions, assisting players with easy hitting and rallying. The art of feeding is one of the things you'll learn on the course and you'll need to practice this.

Chat to a professional coach or club coach or ask if you can watch some lessons so you can see how they're structured.

There's a lot to take in on the  Level 1 and it will show you what you can do. Coach education is an ongoing process.