You are wise to get a block heater installed if you're in a region plagued with sub-freezing winters. A NAPA block heater will work just fine, I had one installed on my Camry five years ago (and almost 200,000km ago) and it still works like the day I first plugged it in.
If you are unfamiliar with core plugs and block heater installation, don't do it yourself. It's one of those few things that just aren't worth messing around with yourself. I paid 45min labour to have it put in--not pricey by any means.
If you
do try it yourself, and you goof it up (no comment on your mechanical ability, believe me), you'll have to tow the car to a shop to finish the job. Getting the core plug out isn't too hard, but installing and properly fitting the heater in the plug hole is tricky. Get it wrong and coolant will leak out around the ill-fitted heater--so you won't be able to drive it to a shop.
Hope this helps.
--Tim
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1990 5spd V6 Camry (Still kicking at 393,000km) 1991 Celica GTS -- Pappa needs a 3SGTE...and AWD for all this friggin' snow
Honda my A$$, you just can't kill a Yota...