There is some free online training, but I don't know about the quality. Google is your friend.
All ERP software is huge from what I've seen, and really learning it is a big undertaking. You could take some training classes but be aware they are expensive. The classes I took for JD Edwards were upwards of $15k by the time I was done. And I didn't take anywhere near all of them.
Also if you're going to make the big bucks with ERP software you're going to have to get on with a consultant like PWC and travel all the time. Really good money but the lifestyle gets old, or so they told me. But those people on implementation teams make big money. Or at least they did when I worked with some of them at a previous job. That was about 8 years ago.
ps - SAP is notorious for being a convoluted mess that is hard to understand. I took a training class with another administrator that worked for a company that implement SAP and gave up on it. I don't know how much it cost them but it must have been a hell of a lot of money and they still said fuck it and went with something else.