I replied in another thread too, but I'll get into more detail here. I'm a degreed engineer, went to a very well respected design engineering school, and worked as an engineer for nearly 16 years. Most of that time was manufacturing engineering (figuring out how to actually build a high volume of parts of very high quality as inexpensively as possible). It was a neat job. I worked on assembly processes, machining processes, plastic injection molding, etc. I've also done quite a bit of product engineering...Not the design side that is artistic, but the engineering stuff where you take the artsy surfaces and figure out how to get all of the marketing requirements into the envelop given you by the designers.
Not saying all that to be arrogant, but just so you know that what I'm going to say next comes from experience. Being an engineer is not like working on your car in the garage. You still work with your hands a bit, maybe building prototypes or setting up tests, but EVERYTHING has to be defined, because your trying to document a repeatable result.
If you really think your dream job will be working for an aftermarket company making jeep parts, there is really only a couple companies big enough to have an Engineering Department (Off the top of my head, I'd guess Currie, Synergy, AEV, Rough Country, JKS/ZONE/BDS, maybe a couple others)...and they are going to be looking for experienced engineers. So, guys (and gals) coming FROM Chrysler, GM, Ford, Dana-Spicer, American Axle, Etc. That means you gotta go to a great engineering school and do really well. Be involved in Mini Baja or FormulaSAE to learn some hands on stuff as well as the book stuff. You need the OEMs to notice you and give you that first job, so you can learn...You don't really learn what it means to be an engineer in engineering school, but you gotta go through it to learn the foundational stuff. Once you work for 5'ish years, you'll start to figure it out, if you have a good mentor. Then you can start looking to the aftermarket.
Anther route into the aftermarket is going to a vocational school and learning fabrication. Get REALLY good at it and go start applying at these places. It will probably mean moving west as that is where the greatest concentration of them are. Once you get hired, work your ass off, be a team player, smile, contribute ideas, etc. Give freely of your mind and body. Apply for ANY move up they post, as well as letting your supervisor know your goals. Eventually, they'll give you the chance.
Those are the traditional paths, as I see them. You could get on a great MiniBaja team and be a suspension whiz. If so, you can shortcut some of this...there are exceptions to every rule. One of my college aquaintances did that at Ford. He did suspension design for our FormulaSAE car, really smart and had great charisma. He ended up at Ford doing suspension simulation for the Explorer right out of the gate...
As far as pay...I started my career in 2000 for 40,000 a year. In five years, I was making about 60,000. Not sure where they are starting 18 years later, but I'd expect it to be 55-65 thousand a year, depending on your location and the job. Your high school guidance counselor should be able to help you figure that out.