It won't be dry unless you overcook it. The pumpkin flesh will give off steam and keep the meat moist.
The meat will pick up some pumpkin taste from the pumpkin, but it won't brown. So you're trading the flavor of browned meat for the flavor of pumpkin.
If you pre-cook the meat, you can get the flavor of browned meat along with the flavor of pumpkin. As Max pointed out, the pumpkin may not survive the long cooking time required by starting with raw meat, so using pre-cooked meat is probably a good idea anyway.
Here's a recipe that uses ground beef, which is first sauteed with onions and green peppers, then tomato sauce and spices added. The pumpkin is also partially-cooked. Then the pre-cooked meat/sauce mixture is stuffed inside the pre-cooked pumpkin, and the whole thing is baked for another hour.
The final cooking presumably allows the flavors to blend and also finishes cooking the pumpkin. The moisture from the pumpkin should prevent the already cooked meat from getting dry and overcooked.