Well, is it a really expensive ticket? If it's only $10 or $20 I would just pay it and remember next time that there's a speed trap there! It IS nitpicky, but you were technically speeding. The only way this might be an issue is if you have a LOT of tickets or are often stopped for speeding, but it doesn't sound like you do.
If you go to traffic court for this ticket it is not going to be a big deal. Nothing to be scared of and DEFINITELY not something you need to pay a lawyer for! Sweetie, the traffic court judge has to deal with so many violations that are so much more serious than this!
It's very likely that the cop will not show up. Cops can't go to court for every little ticket they write. If the cop is not there, it is much more likely the judge will just give you a warning and throw it out.
Either way, just be polite. Don't try and lie- apologize to the judge for going 5 miles over and tell him you weren't paying close enough attention and you admit that, but that the fine seems like an awful lot for just 5 miles over. Most likely, again, the judge will just give you a warning. just be polite - you have nothing to worry about!