V8 Cam Position Sensor -- Any BTDTs?

["Friedman, Jeffrey A" <jafriedman@kpmg.com>]

(Sorry for re-posting the same question again, but I thought I'd give it one
more shot before I'm forced to schedule the car into the dealer):

I have a '90 V8 with the following symptoms:

-- Surging at low RPMs when cold (O2 sensor is 2000 miles old)
-- Slow/sluggish off the line up to about 30 mph
-- Runs great at high speed 

Computer returns a fault code of 'Cam Position Sensor.'  Any ideas
regarding:

-- Where is the sensor (in the distributor or under the cam cover)?
-- How to determine if its a bad sensor, or the cam is off (recent timing
belt replacement)?
-- How do you determine which sensor is bad (or is there only one sensor
between the two cams)?
-- How much fun is it to replace the sensor?

Any BTDTs out there?  Thanks.