So on my friends 08 C30 the mechanic said she needed Struts, LF Axle, Airbag impact sensor, Door inflator module.

I've done the Struts & Axle, where would the Airbag impact sensor be located?
Debating about doing the Door inflator module.

Alos she said her AC will cold for a few hrs the start to get cool or warmer. Would that be that she has a slow leak somewhere or the compressor might be going?

Apologies for all the questions.
Thanks in advanced!