I'm doing this very thing shortly. There's a couple shops in my area (Tacoma WA) that do this very thing. I'm upgrading to a 10k hitch as I will be pulling a 7500# enclosed trailer. With the frame reinforcement + class IV hitch, one place quoted $1600.
With your application and low amount of tongue weight it's doubtful to be an issue. The primary reason for reinforcement/strengthening is the lever affect from the tongue weight.