I would call the manufacturer and see what they suggest. The F-pack is usually used to sweeten the wine AFTER fermentation is completed. Most likely you'll just end up with a wine that's not as sweet as intended. Depending on the kind of wine it is, you could try backsweetening it with something else...but again, I'd talk to the manufacturer first. And there's also plenty of time before you need to do anything, so you have time to get more advise here from smarter people than me.
Another source of information is www.winepress.us. They have a great forum as well.
More seriously just be patient. I'm sure all will go well. As Noontime said, the wine will not be sweet when finished. Some would like that, others wouldn't. You will have to decide whether to sweeten or not. If you wish to sweeten, I would suggest adding some commercial wine conditioner (not grape concentrate) prior to the clearing agents.
How much conditioner??? Tough question. Depends on taste.