hi tophat, both issues are nothing to worry about
. the rear wiper is prone to packing up but this is usually due to lack of use and can be repaired quite easily if you have a bit of mechanical know how
, take off the inner cover off to gain access to the motor (3 screws and pull off the panel to release from the clips) , remove the wiper arm and blade and then undo the 3 mounting bolts to release the motor from the tailgate. once the motor is off there is a small circlip to remove near to where the shaft comes out where the wiper arm is mounted (be careful as they are quite fragile
but a bit of wd40 should ease it out) then unscrew the rear cover. next gently tap out the shaft from the housing out of the back cover complete with its gearing, it is in this shaft housing where it usually gets corroded up and stops things working. once its out, clean out inside the shaft housing with a small file and clean the shaft with coarse sandpaper, dryfit it again to make sure its free-moving and then re-assemble everything with grease to prevent making this a yearly exercise!:bang: it all may sound tricky if you haven't done this sort of thing before but its quite straight forward and logical and is much more satisfying than just buying a replacement new one
. as for the pasenger air-bag, ignore it, your gonna be driving
no seriously an air-bag warning light on doesn't mean you are gonna be going down the road and have it go off in your face
it has most likely been triggered by a drop in current to its control box such as a battery change, probably almost half the cars i see have an air bag warning light on, as its not an mot failure point most people tend to ignore it.
i'm sure its just a case of getting the control unit reset, not gonna be anything major
buy with confidence