@Onan Dumas
You do not need to amend your certificate of formation when you add a new member, and you do not pay a fee per member (there is a fee per partner for limited liability partnerships, but not LLCs). You are not required to disclose the names of the members of your LLC to the Secretary of State. In your Certificate of Formation, you can elect that the LLC be manager-managed and disclose only the name of the manager(s).
Regarding the transfer of the membership interest, if the company is selling new membership interests to the new member, then you would use a Subscription Agreement. If an existing member is selling the membership interests to the new member, then you need an Assignment and Assumption. You also need to have the existing members vote (or consent) to admit the new member to the LLC and have the new member adopt the Company Agreement.
You will need to file an annual franchise tax report for your LLC, which requires you to disclose names of directors, officers and managers.
You should consult a local attorney, or at least call the Secretary of State's Office and ask some questions.
Also, look at these links:
http://www.sos.state.tx.us/corp/formationfaqs.shtml
http://www.window.state.tx.us/taxinfo/taxforms/05-forms.html
http://www.statutes.legis.state.tx.us/Docs/BO/htm/BO.101.htm
http://www.sos.state.tx.us/corp/forms/205_boc.pdf