Its hard to tell without a better discription of "stuff"....LOL
Could the "stuff" be cooked on juices secreted from the meat? And lets just go ahead and change that name from water pan to drip pan. Some folks clean 'em then line 'em with foil, some folks fill they with sand to help with the heat loss. Me, I just wash it out it holds all those drips and the juices.
Let me suggest for your next smoke, try a chicken. Chickens are totally awesome just plain smoked, then you can use it to try all those flavor modifiers everyone wants to do all at once when you first smoke. Birds are cheap, hard to mess up, and unbelieveably tastee!
Jump in and try everything, but myself, I would practice with chickens first a couple a times.
One more suggestion. get a dedicated notebook or set of recipe cards and use it for your education. It really suxs when you knock the ball outta the park on a super smoke, try to do it again a month later and can't get it right. Take notes. Heres some practice pages.
http://www.smokingmeatforums.com/attachments/3
Make sure that when you decide to do something new and fun to research it using the search function. Then if you don't understand or need my help come and ask on the board. Everyone loves to talk about smoking, but its always handy to know something to ask about first.
Well you've started on your way to mastering your pit now, its now about research, experience, and making buddies with a butcher.
Hope ya always think it is fun and remember to enjoy the smoke.
Oh and make sure and sign up for the E-Course its great for the basics!