You need to take forearm off. Take the screw out of the bottom of the fore end, then depress the spring that holds the barrel band and slide the barrel band off. Sometimes the springs get gunk under them and don't want to depress--just be gentle and persevere, but don't force anything. You should be able to see if it goes down enough to clear the band.
Sometimes the barrel band sticks and doesn't want to slide forward even with the spring depressed--a little judicious tapping with a non-marring tool (maybe the plastic handle of a screwdriver) along the top and a little on each side of the barrel can often start it moving. Be careful, and don't hit the band along the wood side, because it can mar the wood pretty easily. Sometimes the forearms drop off, so remove the barrel band over a soft surface, so the wood doesn't fall and get cracked or dented. A couple thick towels on the table should suffice. If it doesn't drop off, a little gentle pulling should free it. If you feel you need to pry it, don't. Instead you should check back here for some ideas on loosening it. There is a metal block on the bottom of the barrel that the forend fits over, so don't try to pull the wood forward--it could come off straight down. The serial number should be stamped lengthwise along the barrel just about on the opposite side of the rear sight.