Ford Focus 2007 1.6

[Andrew Moore]

Airbag light comes on when starting up and disappears but then comes back on intermittently this causes the car to 1 fail to indicate 2 windows unable to open- I think this is to do with the pretensioner on seatbelt but not sure also found the plastic crinkly tube under passenger seat split and a clear tube poking out. How easy is it to replace pretensioners and that crinkly tube full of wires and pipe ?