Rick, we just did the same thing to our 08 Big Sky 340RLQ. I spent ten years doing flooring, and discovered that all the Keystone vinyl is perimeter glued. This makes it easier to lay over an OSB floor which is pretty rough textured. If you are replacing yours then use a good filler on as much of the floor as you can reach and do a full surface glue down. A former employer of mine did our new floor and it looks great. If your 3400 has wood trim on the bottom of the kitchen slide and vinyl under the fridge and stove then pull the wood trim off the bottom of the slide. It is nailed on with 1 1/2 inch brads. Cut the old vinyl out as close to the trim and cabinets as you can. After it is all glued down use a 100 pound floor roller to roll the entire vinyl area. We folded back the dining room carpet and cut the old vinyl as close to the metal strip as we could. We also sanded and vacuumed every bit of dust and sawdust that we could find. Floor prep is the most important part of a good vinyl job. We put a standard vinyl transition strip between the living room carpet and the new vinyl. Here is a
link to my vinyl upgrade. Good Luck... Dave