bladerunner

Hi All, just joined the forum and would like some advice please. I'm putting in a new shower in my en-suite, I'm not an expert but a compitent DIY'er. I've removed the old tiles(put up by builders 16 yrs ago) and found they were stuck directly on to the wall boarding. This is another problem as my internal walls are made of 2" thick straw panels(Strasboards I think they are called). I know I require some kind of backerboard, do I need tanking?(what does this consist of exactly) and can I fix any type of waterproof boards directly to the wall boards? Finally I guess I need to use waterproof tile adhesive and caulk in the corners and for board joins.
Thanks for your help.
bladerunner