Does anyone know of a place to find computers that are not working anymore to mess with at home for learning purposes? Just a hands on thing to see the inside without having to worry about messing up anything.

Just put out the word. There is no one I know who doesn't have at least one or two computers or computer related device collecting dust in a corner or closet.

Put a notice in Craigs List that you willing to collect old, unused computers, old memory, displays, cards - for free, it they are working, fixable. If you are willing to pickup the items, when they are available ... (i.e. - after normal business hours, weekends, etc) some folks would be glad to clear out the old or obsolete parts.
I've been offered enterpise level routers, switches, etc for free (the only thing wrong were a few ports were wiggy or they needed a pwr supply... but I just couldn't handle or justify the energy and cooling costs in a home setup... now if you are taking classes.. that changes everything.

Don't misuse the idea if you really are wanting something current, 2 -3 years old, for free, with an expectation of gathering Primo parts.

also - please don't skim off the cream for stuff that would normally be donated to Goodwill, charity orgs, or schools.

Your only competition might be eBay ... collectors and sellers, who do the same thing - only for personal profit.
There are businesses who buy lots - stoff from companies going out of business, then sell the items at greatly reduced prices. If you check the local classified, you might be able to catch the auctions, before the good stuff is vacuumed up by the big buyers who do the bulk e-bay resale of used parts.

What I did when I wanted to learn about computers is go to yard sales, flea markets, swapmeets and auctions. When you go it really helps to know what you are looking at before you buy. Study your A+ and get some knowledge first! Auctions are good because companies, schools, etc want to get rid of their old PC's but you might have to buy in bulk so keep an eye open. Another good way to learn is to build your own from scratch. Again it helps to know what things are, so study! This could cost a little more and you don't want to screw up. Keep at it and good luck!