Hi and

to both DisBoards and disABILITIES!
If you click on where it says "disABILTIES" at the top of this page it will take you to the Index. One of the top items is the "disABILTIES FAQ" which will gives lots of useful information.
At WDW almost all of the lines are mainstreamed so that a wheelchair or
ECV user will wait in the regular line with everyone else. If there is a sedparatre entrance there will be signs and a CM will point you in the correct direction.
For USO/IOA the following applies:
If you have a handicap tag you follow the signs to preferred parking (which is the 3rd floor of the parking structures; part of that area is set aside for disabled parking. That level does not require use of escalators or stairs.
Shortly after where the two parking structures join together is a location where you can rent wheelchairs. Once you have gone through Security and passed through City Walk and get into one of the actual parks you can then rent an ECV, paying the difference between the wheelchair and ECV prices.
When you leave the park you have to turn in the ECV and they will give you a wheelchair to get back to the chair rental location near the parking garage.
There is a lot of walking between your car and where you get/turn in the wheelchair, and also a lot of pushing that has to be done beteeen the chair rental and the
ECV rental (in both directions)