The fact that he "paced" you becomes a non issue once you go to court and have a witness. If someone goes to court and its the officer and them, then the court will almost always side with the officer if it comes down to one persons word against the other. Now if someone goes to court and they have a witness to cooberate their story, then the courts will almost always side with the defendent. Its a 2 against one senario. If you go in there and play it stupid like you where going home in a normal fashion and you have no idea why this cop pulled you, then you will get it dismissed. That is if your witness backs up your story.
Forget about the "up to 500 $ fine as its rarely ever is enforced. You basically have to yell and scream at the court to get that kind of fine. If one looses its just court costs and the usual fine. I'd say take the chance. The cop may not even show up.

If you do go it will happen something like this. The state(cop) will have to present their case first, thus giving the defendent knowledge of just what it is they are being accused of, and how the state can make such a claim. Basically they are stating their case against you. After the cop tells their story all you would have to do is say....your honor i have no idea what this officer is speaking of. I was mearly going home as any other law abiding citizen would. Next thing i know after pulling out of the mall parking lots is this officer pulling me over. I didn't say anything, or question his/her legitimacy for the stop because i feared for my safety, and the safety of my passenger.
That's all you need to say. The judge will ask you some questions(maybe) and will want to hear from your witness(passenger). If you both have a story that matches and stick to it then the judge has no other option but to dismiss it.

If you don't feel comfortable doing that, then i suggest it would be money well spent to pay 100-300 bucks to have a lawyer rep you. Because you have a witness it should be a slam dunk for the lawyer and may not cost you as much.