Hi,
Yes they have
http://secondlife.com/downloads/avatar.php
And a complete set of texture templates here :
http://secondlife.com/downloads/templates.php
Have not tried using it but my guess is the model will load into AC3D as a single object ... and the templates are assigned to parts of the body. So you are going to have to split the avatar into three pieces (to match the head/upper and lower body).
Since the second life avatars are low polygon poser avs, I suggest you also look at Daz Studio ... available for free here :
http://www.daz3d.com/program/studio/1_0download.php
It may help in splitting the model.
Once the model is split you can then use the three templates and paint your clothes as you wish. I don't think that second life allows altering the geometry (the 3d mesh) though.
If I get time ... I will try it myself as I have all the items I need
griff