Or, you don't have to drill it.

I have a hang-on overflow box which feeds my under-the-tank sump. There are plenty horror stories out there of people having floods, but if you follow
all the safety protocols, you won't have any issues. I've had external overflows for 25 years.
That said, on to filtration. Joe is dead-on with what he told you about your canister filter vs. a skimmer. However, it
really makes a difference how you plan to stock the tank. Do you have ideas yet about what kind of livestock you want to keep? Have you found pictures of "the tank" you want? If what you're looking at is a wall of rock covered in corals with lots of fish action, then it's best to start right from the get-go. If what you prefer is a sparse look, with a few fish, then you will be just fine with a canister, for awhile. Eventually, you'll find that you can't keep the nitrates to a safe level and will ditch it.
I'm not sure about the PetCo test strips. They'll probably be fine, again, for awhile. Once you get things going, you'll see that they won't offer you the kind of accuracy you're looking for. For watching your cycle, they'll probably work just fine.
The most, and I stress, THE MOST important thing to remember with saltwater is that you
must have patience. Yep, it sucks because you'll get excited and want to throw a good sized bunch of fish in there, but slow and steady wins this race. Instead, hook up with some of us locals to check out our tanks. We ALL love to show them off to excited fellow-reefers. It will give you time to ask questions one-on-one, see lots of different setups, get ideas, and help the patience work. Trust me, been there, done that.
Oh, and Welcome to ECRC!