The game needs per-module LIP files for lip sync. Since Selkath use one of the generic fake alien VOs, it should be easy enough to take existing LIP files from one of the Manaan modules and create a new XYZ_loc.mod in the lips folder that matches your module name.
As to the animations, all the creature/monster anims will need to be renamed to their human version equivalents. Some of them should be easy, since they will probably just have CR in front of the same name, but the combat ones will likely be completely different. Since you want to do new anims, this might be a good opportunity for you, since, as you have probably noticed, Selkath lack most of the anims regular humanoids have, so they can't use anything but basic blaster pistol or unarmed attack anims. If you want to make 20 or 30 custom combat anims, then the Fighting Selkath idea could turn into a proper actual thing.