yeah it's doable there are 2 plastic screws on the top where the honey comb grille is that mount the bumper there, then there are 4 nuts that hold it in place through the inside you must remove the fender well to get to these. Then last there is i believe 2 big plastic push in type screws on the bottom you'll need needle nose pliers for that.
If you want the newer 03, 04 cobra bumper, FRPP sells the kit and the installation is pretty straight forward. If you were wanting the 99-02 cobra bumper, I have heard that ford has discontinued that piece and you will have to get an aftermarket one. Im not sure what all is involved in making the aftermarket fit but Im sure it wouldnt be to difficult. You wont need a new hood or anything like that for either one. Here is a link to the FRPP part...
If you are going with a 99/01 bumper you'll have to buy all the parts individually (e.g., fog lights, bezels, etc.) as the previous poster said that kit from FRPP is discontinued.
If you are going with the 03/04 bumper then your problem is hood, bumper clearance. If you do something (I can't remember exactly what it is, do a search on the forums for it) you can get it to line up nicer with the GT hood, otherwise you'll need the matching hood.