Do they have wheelchairs?

Yep. Suggest using tram to get up hills. Easier to go down rather than up.

Does anyone know the cost of a wheelchair rental?

Yes

Yes, they do have a limited amount of wheelchairs available

Yes they do

I am pretty sure they might.you will have to ask them when you go.

First come, first to get one, also depends on what day you go....

Yes first come first served

Yes, on a first come first served basis.