Drill use advice needed

Not a big job, for your sake just read the instructions first. You may need to use a wood chisel to reassess the section the ties to the door jam though, it would look nicer and probably give you more clearance to close the door, you may also consider using longer screws so that the door jam isn't the part holding everything in place. Take your time

for the amount of protection you get with the guardian you could just drill two holes in the floor and take a block of wood with two big nails in it and put it into the holes in the floor so the door will not open.. cheaper than the guardian and you can do it will a drill.....

According to the verbiage, a drill isn't required. So, yeah, a good 12 volt drill ought to be okay.