One tip for ensuring you are not stranded when you arrive: stay on plane and do not exit until the wheelchair is at aircraft door. If you are holding up the turnaround, wheelchair will arrive very quickly. Tell FAs you ordered and are waiting for a wheelchair as you cannot walk the jet bridge.
Also, regarding stairs: if you cannot do stairs but there doesn't seem to be an alternative, find an airline agent and explain the situation. There are usually secure elevators not accessible to the public they can take you on to get you to your destination. Has happened to me many times (I am an amputee and cannot walk).