Sorry to appear to be blunt, but you will have to change it yourself, which is not an easy task. I suggest you have Tyron bands fitted to all your tyres, which if and when you get a puncture your tyres should remain on the rim giving you a chance to drive slowly to a safe spot to carry out the change. Tyron bands are not cheap, but they do give you protection in an emergency. Make sure you have a trolley jack capable of lifting up to two tons in either the van or your car. Maybe if you were to join one of the motoring clubs, EG. AA, RAC , Green Flag they may come out and help you. Hope this helps.
John H