As above you need to have paid back 50% of the agreement to come out without having to pay them to hand it back (normally). Depending on how long into your term you are you might find you need to pay them. Only way to know for sure is call them.
As above, call them for a settlement figure. Just bare in mind that the finance is weighted so you lose more money the earlier you settle. I know from experience that it's definitely not economical trying to get out in the first two years.