Laptops are usually fitted with SD-RAM, which is smaller than standard PC based DDR RAM.
In order to use dual channel they need to be of the same size, and ideally the same speed, although the latter isn't so much of a worry as it will default to the lowest speed out of the two RAM sticks fitted.
With the cost of RAM these days (and assuming your laptop will take it) I would recommend you purchase a 2GB kit consisting of 2 1GB sticks.
In respect to fitting the RAM, its all dependant on how easy the laptop manufacturer has made fitting the RAM. Some laptops require the keyboard to be removed in order to change the sticks, others you can just remove a panel on the underside of the laptop and they're exposed and easily changed.
The RAM is fitted by lining up the stick at 45 degrees to the socket, and then sliding it into the socket til resistance is felt, then pushed down til it locks into place on the metal clips. To remove the RAM, you just spread the metal clips on each side of the stick, and it then pops up. You'll see exactly how its done when you remove your old RAM sticks.
