Default [Q] Selling Note 2, keep root and rom, delete data


I am selling my Note2 for financial reasons (getting another tho!). The seller wants to keep the root and rom I have on it now (Synergyrom). I have never done this before, just returned to stock...what do I do? How do I properly do this to delete my data and make it fresh WITH the existing root and ROM??

I should also mention, she doesnt care about the KNOX warranty thing...its out of warranty anyway.

Thank you kindly,

Sprint Galaxy Note 3
X-Note V15