The aftermath: I contacted streetkeys.com (Manny=owner, nice guy) and found them to be very helpful. Basically, you pull the ECM (located behind the glovebox on the '00 LS400), mail it to them along with a copy of your title/registration and driver's license and they ship you the keys you specify on their website. Good prices and fast service were promised. That, coupled with a money-back guarantee, and I was heading in their direction.
However, I ran out of time and found someone who could come out to the house and take care of it. I paid $300 for his services and a single master key (without keyless entry, etc). I await a price on a keyless entry model key but he expected it to run around $180 cut. That would put me at $480 for a master key and a keyless entry key.
Dealer cost was $550 (2-keyless entry keys $225 + one hour labor $105). The dealer told me that there are only four ECM's in the country and it would take about a week and a half to get it to their dealership (in MI). I probably would have gone that direction for a few bucks more if they'd had one in stock.
Oh yeah, I checked my insurance too. Evidently they don't cover stupidity. lol
Thanks for all of the help. Much appreciated!
EDIT: One key difference between using the non-dealer locksmith and the dealer was the ECM unit itself. Lexus will replace (one time ever) the ECM for the current owner of the vehicle. Their cost is around $1600 to do this and they require that you purchase the two keys and charge you an hour labor. Why they don't just "zap" the security chip on the Module like the locksmith did on mine is beyond me. This means that you would have a new ECM in your vehicle which may be enough to sway some in that direction.