This happens all too often, tracking adjusted on one side instead of adjusting half the amount on each side results in steering rack no longer being central.
If the tracking is done correctly there is no need to ever move the steering wheel.
I haven't needed to remove an airbag from a freelander but it'll be much the same as any other, disconnect the battery, wait 10/15mins for system to discharge then remove fixings and disconnect the wiring.
Or you could take it back and ask them to centralise the rack.