Have the lease option documents notarized really helps with this process by the way. 

If it is notarized, than you recording the contract will be super easy.

Notarized, recorded, official and everything. 

The deed and certain closing docs (i.e. anything that would be recorded at the county courthouse)  should be notarized but an assignment of agreement of sale or an agreement of sale usually aren't notarized to my knowledge, just witnessed.Best,Dave

The structure seems fairly straightforward (as stated above), he and I will sign and have notarized the warranty deed and security agreement.

Is it as simple as drafting up a promissory note with the agreed upon payment schedule, getting it notarized and paying $150 or so dollars to transfer the deed? 

As for private lending, you always need these items: Promissory Note signed and notarized, Joint Venture Agreement, and a Deed of Trust or also known as a Notice of Interest in some states that references the Promissory Note and JV Agreement.

We have an option contract that has a provision to get it notarized & I am wondering if that is really the case.

Send a notarized invoice along with a letter from your attorney, he may draft one up for you for few bucks. this way they know you have already started the process and are not fooling around. send it certified mail

To determine if the quote is good price or not: are you insulating the garage, are you running electrical, assuming standard one entry, are parts included in any?