Introduction to Geology Books
I believe Manual of Mineralogy (based on Dana) is a good start for mineralogy and crystallography subjects. It is a good manual to understand the basics behind crystalls and minerals. It is a bit theoric, but it explain crystallography laws you need to know to face microscope. It also list the minerals by groups following Dana classification.

I would recommend to chose recent introduction books to get a view about Earth Sciences in general, as modern tectonics has changed some concepts. That will cost you some chips; if that's a trouble, university libraries use to be open to public. You can go there and read any book published recently whose title look like "Introduction to Earth Sciences". There are some books that specifically have a geophysics approach. 

Talking about studying geology at a post-secondary level would be like, you need to know in geology field is the lab. In firsts courses you might find difficult to get it, but once you got the basic concepts, you will start to enjoy the Friday trips.

I am going to recommend, if you have the opportunity, to join a geology summer camp. You can ask at the university you want to join if they have field introductory courses. You will need good shoes, a geology hammer, a compass, a magnifying glass and good attitude to learn new things.