Gary, normally, the shutoff is near the source of water supply which is directly behind the UDC (universal docking center) You will have to remove a panel of the basement wall. There are 2 or 3 screws you will have to find to remove this panel. Once inside, look for the 1/4" line and there will be a valve. One day they might make this a more accessible valve...
Regarding the drawer that won't come our far enough, pull the drawer out as far as it will go and check on the slides. You should see a small black plastic lever. On each side, one lever goes up and the other goes down. These are spring loaded so you'll have to hold them to release the drawer and pull out at the same time. When reinstalling, they latch automatically.