Wow. You're new around here. Cross party lines? Heresy!
You're about to be introduced to the wrath of the NJLP. I won't steal their thunder here, and I hope you have thick skin.
I, on the other hand, encourage you to pursue your plan, and urge you to ignore the fossils here that are more interested in promoting the Party than liberty.
Don't be disappointed if the Dem "machine" doesn't instantly love you because you have a "D" after your name. Unless you've contributed to / held fundraisers for the current leadership, you most likely won't make it past the screening (pre-primary vetting). And, if you haven't kissed the ring, they'll support another Dem that has. Also, go find a D committee member in your town, and try to get elected to that. There are almost always empty seats, and an appointment is very likely. Once on the committee, getting screened will be much easier.
Also be aware that hijacking the party in your town won't escape the notice of the County and State orgs. They would rather endorse a Rep and teach you a lesson than allow you to criticize Corzine.
<obligatory>Or move to the FreeState and be appreciated for your activism.</obligatory>
I'm waiting to see what you have in store. Keep us posted, ignore the purists around here, and keep your eye on the prize.