I need bath remodeling suggestions.

I just bought my first house. I have paralysis on my right side and for years have had to deal with stepping into the tub to use the shower. My new house has the standard shower over tub and I see three possibilities.
1. Install grab bars (cheapest and fastest).
2. Replace the tub with a big shower with a bench.
3. Get one of those walk in tubs.

For 2 & 3 I would be interested in comparable installation costs. Does anybody have experience with the walk-in tubs? What would be the downside to 2 or 3?