I'm doing the same thing to a very similar sized pool.

In my case there are dozens of layers of plaster.

The key is surface prep regardless which direction you decide to go with.

I started with my stairs which are the worst. A Hammer and chisel to get some of the delaminating layers down to something solid.

You'll want to drag a hammer or bounce a golf-ball around the pool to see if there are any hollow sounding spots and chisel them out.

If you decide to replaster see this link: http://truetex.com/pool.htm

Other options include:
1. a Vinyl liner - May not be possible with your pool and you have to get a smooth finish anyways or it will show through the liner
2. Hybrid Epoxy - I'm strongly considering http://www.poolrestoration.com/
3. Fiberglass - There is a do-it-yourself kit from uglassit

For surface prep I'd look into a "scouring machine" specifically for removing plaster from concrete.