Most of the guys here will tell you the original style carter or Kohler carbs are the best carbs. The walbro's don't have full ability to be adjusted and the floats are plastic and they usually have problems with the valve the float works. Also they tend to use more fuel than a Kohler carb.
Unless something was broke in yours you should be able to rebuild it in a day or so, giving it time to soak in the cleaner solution altho a lot of guys including myself use carb spray cleaner and an air hose to clean out the carb. They are exceptionally simple to take apart and put back together. The one thing to check on yours or any other one that you buy that is used is if the throttle shaft has some play it in around where it goes thru the carb body at the top. If so I did a write up of what you need to do to fix this with a couple of CHEAP parts you can buy at your local hardware store or can order.
A lot of times this slop in the shaft will cause an unstable idle or surging. Other than that, the rebuild consists of a new float and valve, float bowl gasket and seal. We have some good write ups on how to do the whole thing.
Here is the link for rebuilding:
http://mgonitzke.net16.net/tools/carb_rebuild.pdf