Compare the length of the old chain to the length of the new chain and find out how many extra links you have. You should be able to get away with about 2-3 extra links but you will still run the risk of it slipping off if your not careful.

Try not to use the front granny and stick to your biggest gear (high gear). Meanwhile the rear derailleur should be able to manage the slack on everything other then the highest gears (smallest).

The other thing you could do is take the old chain to the bike shop if it's near by and have them size it quickly for you and pop off the extra links.

As for the quick link it's fine to use it and will work with any drivetrain as far as my understanding goes. Never heard of anyone running into too many problems with them aside from some complaints that certain makes will wear down faster then others. Their mainly used to help in maintenance of the chain or to work on the drive train. It allows for quick removal and prevents premature wear on the rivets caused by chain removal tools.