You really need to sit down face-to-face with your tax advisor so you can go back and forth in real time to explore your issues. Some starting questions for you to discuss would include why your partner is willing to accept a stock sale when an asset sale would be more beneficial and less risky (unknown liabilities, etc.) to him, why you're not selling him 1/4 of the stock each year, what are the terms of your non-compete, is your lawyer sitting in on your meetings, will his lawyer and tax advisor join you to work out the sales contract details, what other types of income you (and your spouse, if married) expect and what amounts over the next four years, what you will do if your soon-to-be-ex partner defaults, etc. Your tax advisor's questions will depend on your information to him and cannot be predicted in a vacuum. You can find lots of reading material online and in a good business library to bring you up to speed on the generalities.
This is a site where tax professionals discuss tax issues among ourselves. As you said, no one can know everything, so we can get advice from and share with colleagues, especially those that use ATX tax prep software. Your tax preparer may be here. Do you really want him to think that you trust him so little that you had to start with other pros before him!