The yeast will ferment the wine to dryness. There just aren't any of those long chain maltodextrins that they leave behind in fruit juice. So, a 7-10% wine is one that starts around 1.060-1.075. Find a quality source of juice, measure the SG of that, then figure out how much sugar to add to get you into the range you want.
Now, adding the sugar back at then end is something I haven't tried yet and information on how to do it successfully is sketchy. But, you have months before you have to worry about that ;-)