Hi,
Points 1 & 5 -- Better answered by those who have done this recently.
2 - What should I expect to pay in registration/tariffs/taxes/import/duties on my vehicle once I pick it up in the UK?
It should be free of import duty if you've owned it more than 6 months and are bringing it over to establish residency.
You'll still have to pay the registration fees, which includes your first year's "road tax" (equivalent of license tags). As it's a 2000 model, the latter will depend upon the engine size/quoted emissions.
Unfortunately, as well as having to undergo the regular annual vehicle inspection (the so-called MoT), vehicles less than 10 years old being imported now also have to undergo a "Single Vehicle Approval" test unless the model already has a European type approval. I've never had to go through this myself (I much prefer older cars), but I understand from those who have that it can be quite complex and bureaucratic.
Start here for some information:
http://www.direct.gov.uk/en/Motoring/BuyingAndSellingAVehicle/ImportingAndExportingAVehicle/DG_40225833 - Would it be easier to sell our car here in the states and purchase/lease something over there?
Unless the vehicle is something special and thus worth the trouble and expense, quite possibly.
4 - How soon after we arrive do I need to obtain a "local" UK drivers license?
Within 12 months of establishing residency. Unfortunately, for those with a U.S. license it also means having to sit through
all of the tests required of a novice driver here -- Written rules test, a hazard-perception test, and a practical drive. Have a look in the Transport & Travel section for several threads discussing this.