It isn't at all risky, though I imagine if you havnt done it before it may sound daunting. The battery is held in with a little clip at its base. Push that in (a pinky finger should suffice) and the battery will pop out.
The location of the CMOS header will be detailed in your manual, with instructions on how to short it.
Basically, all you need to do is make the connection between the 2 pins, which is done by moving a small connector called a jumper across from one set of pins to another.
It may look something like this (if this makeshift diagram helps) the "I" represents the pins while the "_" represents the jumper, the full stops are there just to make it space correctly:
._
I I I this is the jumper in normal mode
..._
I I I this is where you put the jumper to clear the CMOS.