Sal
I am so happy to hear you are being pro-active about your living situation. I truly believe that you will be able to stay in your own home for as long as you want with some work on the hardware!
I think the ramp will be the biggie. You need to be able to get out in case of fire and three steps down is not a steep grade, so it shouldn't be too expensive. Maybe you could just have a landing that extends to the door of the van so you can walk right to it and a short ramp that extends from the side to allow access to the garage and outside.
The bars are easy to install, the handyman just has to find the studs and screw them onto the walls where needed. Think about where you use the walls and other stuff to grab onto and put in railings and bars at a height that will work for you now and later if you find yourself sitting and rolling.
If you don't have a shower bench installed yet, think about how you will bathe and get in and out of the tub if needed. A fold out wooden bench can be installed without much retrofitting. It screws to the inside wall of the shower/bath and should be long enough to reach outside of the tub/stall so you can transfer and slide across it into the tub/stall area. A hand shower is easily added, even two or more if you need them!
I've been doing a lot of thinking about this very subject. I am trying to make my remodels user friendly with the objective of staying in my own home 'til I am dead. Everything I plan includes handicapped accessible, ease of use and cleaning!
Please keep us posted!
I am looking forward to seeing what you come up with!