It's doable. Usually just takes a small Phillips screwdriver and a lot of patience. Be a good idea to take a lot of pictures as you take it apart so you will be sure to get it back together. Helps if the screwdriver is magnetic. Always a chance that the new motherboard is no good so you might have to back it out.
If you get a used one, use Speedfan to verify that it is not running hot:
Download, save and Install it (Win 7 or Vista right click and Run As Admin.) then run it (Win 7 or Vista right click and Run As Admin)
It will tell you your temps. If they seem hot (over 50)
You can also use Speedfan to check the hard drive:
In Speedfan, click on the S.M.A.R.T. tab and then on the down arrow to the right of the empty box. Select your hard drive. (Only one there on a laptop). This will show you the info on your hard drive. It should be all green OKs (or nothing for info only things) other colors indicate problems. You can also click on Perform an in depth online analysis of the hard drive This will open a webpage with more details.