you need to take the clamshell apart battery is soldered to the pc baord , as I recall there is a duagte baoard you have remove to get at the battery (or maybe the batt is on the daugter board ,its been a while I dont realy recall ,but you will see it there )
battery cost around 6.00-10.00 range
can you do it ?
well that depends on your comfort level with pc board soldering/ desoldering .