I took an early distribution from my 401k. Like everyone else, my value dropped dramatically from the days when I was actively contributing. When I complete my tax return, should I be trying to obtain the tax basis to show the loss incurred and thereby (hopefully) reducing my tax liability?

It doesn't work that way... a 401K isn't a capital gains issue good or bad. You don't pay extra because good times, and you don't get credit in bad times... you simply pay for what you took out at the tax bracket you are in at the moment... and if its early the penalites as well.

401(k)s are tax deferred. This means you don't pay taxes on it until distribution. Therefore, no tax basis or capital gains.