It will all depend on the weight of your plow setup. The more weight, the more you need to beef up the front suspension.
Decide on what plow package you are going to get first and that should help you determine if your suspension parts are enough to keep it from sagging too much. If you plan on getting a quick connect/disconnect plow (which I highly recommend), then only put the plow on when you are plowing (or the night before a storm if you are informed) and just keep the plow mounting kit on all the truck at all times with the plow removed when your not going to use it. Removing the plow in between uses is the best way to go as it will save on your front end when driving. If you plan on removing the plow between snow storms, then your current front end components should work just fine.