Air bags have gone off on a a motor that I'm thinking of getting, just wondering how hard is it and is there anything I need to know to make it safe and easy?

you probably won't have to change the dash,what car is it? because if its a mk4 golf i have both airbags and the control module for sale and the swap is very easy,if you do have to replace the dash then it will be a nighmare,but i wouldn't have thought on a modern car this would be the case

But if it's popped a hole in the dash!

they don't pop holes inthe dash normally,where the airbag comes out is actually a pop out bit of plastic and shouldn't damage the dash on airbag deployment

Pretty sure when the passenger airbag goes off it rips a big hole in the dash, so the whole thing needs changing. It's not "too hard" but you will need to be thorough when it comes to removing / refitting everything - I've done it twice now. Start with all the gubbins in the centre console, remove the steering wheel and lower trims/glovebox. may as well remove the gear lever centre trim out along with the "C" shaped bit that connects up to the dash. Then it's just a few bolts, couple at each end from memory and a couple in the middle, at the back.