The guide above is good but misses a lot of stuff, bare this in mind you will proably want to refer to the twinspark service manual aswell.
Its a fairly big job but mainly annoying more than anything. The variator is a swine to get off and you will need to replace belts and while you are at it replace tentioners and water pump so it can be expensive.
I would also take the camshaft off to replace the variator, don't take the chance using cam locks. It can be done in situe but its really not worth it in my opinion.