To change two of a vehicle's tyres normally takes between thirty and sixty minutes. The time to change all four tyres is approximately forty-five to ninety minutes. This is based on the presumed workshop activity. The time to change tyres could be extended by the replacement of valves, hard to remove wheels and wheel cleaning and by wheels that have seized nuts.
The availability of next day fitting will depend on the size and type of the tyre required as well as the local fitting service availability. It is safer to book the very first appointment if you have tread which is near the legal limit, has cracked or has bulging. Until you fit these tyres you should avoid long distance journeys and excess speed.
As long as a tyre has not been run flat, a puncture in the main tread can be repaired. A side wall puncture, any damage in the sidewall and/or a large puncture or damage caused to the tyre on the inside will normally mean the tyre has to be replaced. Do not drive on a tyre that is losing air pressure.
It is highly recommended that the wheel alignment be checked if you have struck a kerb or pothole. Alignment should also be checked if the steering wheel is pulled to one side. This ensures even wear of the new tyres and reduces fuel consumption.
You have either option available to proper size van rated tyres. One, is to check your registration and input the correct size. The other is to check sidewall markings of the tyre. Vans carry more weight since they are used for transporting stock and tools. Safety, stability, and longevity of your tyres improve with proper specification.