Rosie, installing your own tile is doable, but will require some study. The first thing to know is: don't install it over a hardwood floor. You'll want to remove the hardwood and install tile backer bd. You can figure some combination of underlayment/backer bd./tile that will bring the finished floor back up to the same height. For backer bd. the floor structure needs to be: joists no more than 16" oc, with a min. of 5/8", but preferably 3/4" or greater, plywood.
Since this is apparently your first tile job, I suggest you get a copy of Setting Tile by Michael Bryne (his Floors video would also be helpful).