Heres a link to a "easy" way to replace the cam sensor magnets-
http://bellsouthpwp.net/p/a/padgett46/cammag.htm
Its pretty common with this era of 3.8's. Usually happends when you get "frisky" with the rpm's
I'd also highly reccommend swapping to the newer style ignition coils. I did on mine & got a couple extra MPG out of it, worth every penny!
http://bellsouthpwp.net/p/a/padgett46/coils.htm