Push Button Shifting Part 2

ok i made a post back about a month ago asking if it was possible to install a push button shifting on an auto trans like the new Grand Prix have or the Lincoln LS's. Well i found something that will do it for me, seems pretty simple and relatively cheap under 500 bucks. Im just interested in how hard do you guys think it would be to install and any other recomendations. Heres the link.

http://www.levelten.com/store/gm/items/electronics/gm_shiftronic.htm

they say its a plug and play device, so i cant see it being too difficult. i assume its going to be a module that piggybacks onto the computer, with buttons mounted in the cabin. since the computer tells the tranny when to shift, there shouldnt really be any mechanical parts to be installed. if all else fails, im sure a mechanic would be able to figure it out with relative ease.