Everyone else pretty much summed it up...take em to a shop.
Jig is necessary!
Bit size is dependent on ski not binding.
If there is no metal in the ski...then you typically use 3.5 x 9.0/9.5
If there is metal in the ski....then you typically use 4.1 x 9.0/9.5
This is very general as well. bit depth is largely dependent upon mounting position as well as ski and screw length.
A 40$ mount is a lot cheaper than new skis!
Always remember to check the two finger fit!