Not quite.
If you forced a sale you couldn't account for the 'goodwill' if the goodwill is now associated with the others partners new business. You will only get what someone will pay, and if the business is now trading under the other partners trust, nobody could buy the business? If that makes sense?
Your best bet is to get a lawyer - not kidding, even a low profit margin over many years can add up to be a substantial amount, any claim over $70k goes through the state supreme courts, so not something you want to go into unrepresented - possible, but not advisable.
Your 'next best bet' is difficult to say without full knowledge of the situation, however from what I can understand of the situation, I would -
1. Attempt to contact the other business partner, offer one last chance to arrange an amicable resolution to the situation before you seek legal advice. They may be willing to pay an acceptable amount to have this over with.
2. If unsuccessful, I would send a letter to the other partner advising of my intention to leave the partnership and advice a letter of account which I expect to be paid will follow.
3. Gather up all of your accounting information, figure out what you want $$ wise, send a letter demanding that amount with x days.
4. Commence proceedings at the Courts if the partner did not reply.