you should buy a torque wrench if you change the oil or not. They are an important tool for anyone who ownes a motorcycle. Youll cover what you spent on it in one or two oil changes.
I torque the bolts to spec.
I,ve done a lot of work on harleys over the years and never owned a torque wrench. I've watched techs at 3 dealerships work while I was hanging out and do not remember ever seeing anyone use a torque wrench.
A torque wrench is a nice investment, and they're not expensive at all. Go for the clicking type, they're a bit more expensive than the gauge one but worth it. However, I've done oil changes without torque wrenches before, just be really careful not to strip the drain plug.
BTW, I'd also get an oil filter key for $10 bucks, I picked mine up at my Yamaha dealer. It helps take the old filter off and allows you to torque the new one to spec. And get some hex inserts to clean or change the pickup screen while you're at it.
My Ducati dealer charges me $100 per oil change, I'd say I recouped that after the second oil change that I did myself even including my time spent and money invested in tools.
Definitely an easy do-it-yourself project on the monster. Not even any bodywork to takeoff! ;D
By the way, to check the screen you need a LARGE hex/key socket (can't remember the size, may be in the FAQ). Most stores only go up to a 10mm. My Sears didn't even have one. Found a cheap set at Auto Zone, of all places. Had 3 larger sizes for drain plugs.