Hi, JRoss. Sorry to hear about your troubles. Doesn't sound like fun at all.
I agree with bigblock4speedman, you and your mom need to sit down an have a serious talk.
You mom seemed pretty cool. I remember her taking pics of a Challenger she saw in a parking lot.
What's happened since then? Your mom seems like she's pulling some pretty drastic stuff on you: She wants to sell the Cahllenger, truck, and kick you out of the house? These things don't happen over night.
You're 18 now and maybe she's concerned about your future. You don't have to say here, but does your mom know what you have planned for the future? I think you graduated highschool recently, right?
Any parent would want a bright future for thier child. I know I do for my kids. Maybe your mom is just looking to see what your sense of direction is at this point in life. Have you had a nice sit down chit chat with your mom? This doesn't mean a shouting match. If your mom is the type that likes to have control, you're going to have to hold your tongue and do a lot of listening.
You're 18 and an adult but you're still under her roof. I have a single friend that just moved out of his parents house at the age of 34. Man, was it tough on him. Only child and mother VERY controlling. Now he has a breath of fresh air. But he's pretty established with his job and all.
Take some time and let you mom voice out what she has to say. Listen to her talk and see what's right for you.
If all fails, see Plan B that chrisII posted above.