This may appear to be a dumb question but here goes, my loan is a true refinance under HMDA definition but it is a fix rate so is my rate spread going to be NA?

You need to do the rate spread calculation.

Not necessarily. If if the APR at consummation, whether an ARM or a fixed rate, is more than 3 percentage points (5 if a subordinate lien) above the comparable treasury security for the term of the loan then you have to enter the spread. Assuming your loan is a loan subject to Reg. Z, otherwise the spread would be reported as NA.