You can book a cab easily and I guess it would helo you out.
However, I would suggest you to visit Goa and then book a tour as it would help you in negotiating the price.
Face to face negotiations are much better compared through an email.
Note: there are lots of tour agencies. So finding them is not at all hard.

Plus to book a cab you may… Read more

Yes, you can access Taj Mahal and most of the places through wheelchair.
However, the main tomb is not accessible. Toilets are also accessible.
However, I have seen people using locals to carry their wheelchairs and them in the tomb as well by paying some Indian rupees.
Can’t say how much as I have only seen it.