First of all, be carefull what you write, dont provide the rope to hang yourself .
Secondly there is no reason why, if properly entered, your terrier should not do foxes(if he is off working lines). Chances are he wont, but you will never know if you dont try.
Third and most important either go out with someone who knows what they are doing, or buy a book and do your research.
Last of all, you are about the back end of the season, so that gives you nearly a year to do some research .
FTB