Hi, Mike - Chris will probably chime in here, but this is NOT a Weber-sponsored site. Not connected to the company a'tall. Chris Allingham was good enough to set this site up for all us WSMers to share information with each other. As a user and NOT a company rep, I (and many others both on this board and throughout the home and competition barbecue community) will tell you that you can't beat a WSM, because of the air-tightness and outstanding ability to control temperatures. Let's see if I can address your questions somewhat:
1 - temp range: I have smoked cheese at 90 degrees, and I have baked biscuits at 425. I regularly do chickens or turkeys at around 350. It holds at 225 - 240 as well as an oven once you get your vents set right.
2 - No. You'll want to mop from the top. Even more advisable is to use a mop with no large spices in it, such that you can use a spray bottle instead of a mop or brush. You knock off less rub that way.
3 - There will be no need to "change out coals" with the WSM. Jim Minion, a competitor from Washington state, came up with an approach that you'll see called "the Minion Method" or MM for short, whereby you fill the charcoal ring with unlit charcoal, and place a few lit coals on top (I count out 15 to light to go on top, others use 1/4 chimney... whatever works for you). You then place your waterpan and meat on at the that time, and control your heat as it rises. 18-hour cooks with no charcoal additions are very common-place with this method. Yes, you can add a few pieces of charcoal, if you need to, through the access door with tongs, but very rarely should you need to.
Sounds like you've cooked on an ECB (El Cheapo Brinkman) before - the difference in temperature control on a WSM and on other bullet-style water smokers is like day and night.
As the shirts available for this site say, "Buy the Best, and Only Cry Once". /infopop/emoticons/icon_biggrin.gif
Do I hear an amen from the choir, dearly beloved smokers and smokettes?
Keri C, smokin' on Tulsa Time