Sorry to hear about the accident.
Here is a
link to the disABILITIES FAQs thread.
There you will find information about the different ways of getting a wheelchair, including getting one lent by your resort, renting at the parks, or from one of the off-site medical equipment companies. The FAQs also includes somme of the pros and cons of getting one in all the different ways.
The wheelchairs from the resorts can't be reserved ahead of time, they are first come, first served. Some people have had good luck with them, but others have found that there were none available when they arrived (as one of the posters on this thread found) or the wheelchair that was available didn't meet their needs (extra wide when they needed regular, or vice versa). If you do decide to try for a resort one, it is a good idea to take the contact information along for one of the off-site rental places, in case you need it.
There are 2 types of handicapped rooms. The first type have raised seat toiles and tubs with grab bars. Other than that, those rooms are the same as a regular room. You can arrange for a shower chair if needed.
The other type of handicapped room is fully wheelchair accessible. It has grab bars and a raised seat toilet, usually has a lower bed, higher power outlets and light switches you can reach from a wheelchair. Those rooms also have roll-under sinks and a shower that a shower wheelchair can roll into. Thistype of room would probably not be a good choice for you. The shower has only a curtain and if the shower head is not aimed quite right, the floor can get wet and slippery.
ECVs are rented in the parks (first come, first served), but no guarantee that one will be availble when you arrive or if you park hop. Power wheelchairs different than ecvs; they are driven with a joystick (or other access device for people who need other access) and are more difficult to drive than ecvs. They are only rented by the off-site companies; and only to people who already have a power wheelchair, but didn't want to travel with it.
Most of the lines are wheelchair accessible (they call this Mainstream Lines) and people using wheelchairs or ecvs, for the most part, wait in line with everyone else.