I recently found a small water leak in my finished basement when I removed a large section of wall board. I was able to stop the leak. My problem is that the sill plate has some rotted wood from the water now. The rot is not all the way through, some places are worse than other. I would say the rotted sections run about 12 feet on a 30 foot run of wall. They are mostly concentrated on one corner where the leak occurred. At the worst spots the rot goes approximately 1/3 of the way through the sill plate. My question is: How bad does the sill have to be before it needs to be replaced? Would I have to replace it all or just the rotted parts? Is this something that a handy guy like myself could do?