Im going to give you some advice learned from being nearly a decade older than you. You can choose to ignore it, take insult from it, or whatever, but I promise you its well meaning input that I would tell me own son if he presented to me the facts you laid out above.
If you're obligated for $26K on a 2 year old V6 mustang and considering trading it in, you are so underwater the edealer is going to slide it in so deep and rough that you wont walk right for a week after. You are going to have $10K in negative equity before you even start talking about the new car. You do this switch and you're easily going to be $45k in debt when you roll out of the showroom. Now I dont know what you do for a living or who you are but I do know the average 24 year old in Michigan makes thless than that as a annual median income.
Also what is the length of your current loan that you are only paying $350 a month? Did you get a 72 or 84 month loan?
My honest take is that you are making financially irresponsible decisions.
I quoted this post for how much truth it contains. I was in a similar situation as the OP when I had my 2007 GT and traded it in on my current 2010 GT.
I really wish someone would've given it to me straight just as the post I quoted. Sure, the 2010 is nicer than my 07 was, but the financial side is somewhat ugly.
By the time the negative equity and all the other charges were added on to the 2010, my payment went up $80 per month for a 75 month term. I'm in so deep refinancing again would be financial suicide.
The good thing is that I learned several valuable lessons:
1. Never sign papers the same day you look at a car. Think about it.
2. Read everything before signing anything. Dealers can be sneaky.
3. Never carry over negative equity. Pay it off, then trade it in.