Hi, my last car's exhaust fell off two days after smoke had issued from the steering column for a minute or so, forcing me to make an emergency purchase - my brother's '99 A3 1.6.
It's lovely to drive and quiet as a mouse despite 85k on the clock.
It does have a fault, though, and I'd like to upgrade the stereo to play CDs...

I have the ubiquitous airbag light on problem.
The fault code says the passenger airbag igniter resistance is too high. OK, I thought I'd get the VAG dealer across from work to quote for them, only he only quoted for the airbag... and Googling the part number results only in a few foreign websites.
Is the igniter part of the airbag?
I've read about bad connections causing this all over the place in the last few days; would I be looking at wiring behind the dash or is the connection under the seat associated with the dash airbag?
Are there loads of different airbags fitted or can I grab one from any A3 of the same vintage? Should I get a number off the unit and search for that?
The car was fairly cheap (as this model seems to be in general) and it'll last me a while, so I wouldn't begrudge the couple of hundred to get it from VAG if that's my only option, and if buying it will extinguish the light and pass an MOT when it comes around.

Next question seems to be asked everywhere and no-one has a definitive answer...
How do I know whether the factory stereo is Bose amplified?
How do you tell whether it's rear-only or fully amped?
There is a sub in the boot behind the N/S panel.
I haven't removed the head unit yet as I am out of the house between 6:30am and 7:15pm during the week and planned on installing the unit over the weekend.
Do I just need to pull the unit and take a look?

Any advice would be greatly appreciated.

Cheers,
Chris.