from one enthusiast to another please research more before making purchases, you are experiencing the stress caused by lack of research. whether you would have made the purchase knowing the condition of the car or not is somewhat irrelevant as the big hit is that you are not prepared for it, nor are you well equipped to talk to anyone intelligently about a resolution.
what you are doing right: your attitude here shows you are willing to learn and that is great! it is very important to keep this attitude despite the trolls out there.
it is not too late to get up to speed on how your car works, but i think you need to bring it back to stock and pay it off. until its paid off, consider what you honestly do not like about the car, and then research the best way to make modifications. if you understand all risks and are prepared, you can be stress free and will not need to beg and plead for advice on message boards.