Congatulations Mike,it's just so much sweeter to find a nice plant already in your yard than importing somthing to plant.
I'm no grape expert either but I try my best until one arrives.
Are you 100% certain the vine hasn't been there all along? That's important to know because almost all desirable grapes are grafted and you mustn't ever cut it off below the graft . Regardless of other considerations you should remove most top growth once vine is dormant. This is will give you a general idea and hopfully an expert will come by and give the actual instructions. You will need two sturdy 5' tall posts 15 feet apart with vine roots centered between posts. Two wires stretched post to post at 3' and 5' above ground. The goal is to train a single leader(trunk) from ground to top wire with 4 branches reaching down wires. Grapes produce best on last years growth so choose this years growth to train on either wire to produce next years crop. Hopfully one of the 8 vine(branches) can be tied up to form a single trunk from which all future growth will origionate from. The wire that remains vacant after tieing young growth on other reieves 2 healthy branchs,one going right,one going left. These last two branches are cut 6 inches to 1 foot with 1 to 3 healthy buds on each and all remainig branches lieing on ground are cut flush with central trunk or ground. What you should now have is two young limbs 3 to 8 feet long tied to upper or lower wire plus 2 stubs with buds on other wire. Dormant season 2015/2016 the 2 year old branches are cut back to a few health buds and 1 year old branches are miniumaly groomed and left to bare fruit in 2016. You will have fruit on one wire each year while the other wire grows vine to produce following year. It seems odd to cut away more wood than you leave but the fruit will hang thick and heavy on less wood rather than scatered amoung a bunch of long vines.