The following answer is based solely on the background question provided as we do not have all of the facts and information pertaining to your contract or contractor. As we do not have access to the contract folder or program particulars that apply to this situation, we highly recommend you consult the Contracting Officer as well as your Legal Office. Your situation appears to involve whether or not exercising an option would require a D&F.
The answer is yes; see D&F included below and reference FAR 17.207(d) and DFARS 217.207 below:
17.207 -- Exercise of Options.
(a) When exercising an option, the contracting officer shall provide written notice to the contractor within the time period specified in the contract.
(b) When the contract provides for economic price adjustment and the contractor requests a revision of the price, the contracting officer shall determine the effect of the adjustment on prices under the option before the option is exercised.
(c) The contracting officer may exercise options only after determining that --
(1) Funds are available;
(2) The requirement covered by the option fulfills an existing Government need;
(3) The exercise of the option is the most advantageous method of fulfilling the Government’s need, price and other factors (see paragraphs (d) and (e) of this section) considered;
(4) The option was synopsized in accordance with Part 5 unless exempted by 5.202(a)(11) or other appropriate exemptions in 5.202, and
(5) The contractor is not listed on the Excluded Parties List System (EPLS) (see 9.405-1).
(d) The contracting officer, after considering price and other factors, shall make the determination on the basis of one of the following:
(1) A new solicitation fails to produce a better price or a more advantageous offer than that offered by the option. If it is anticipated that the best price available is the option price or that this is the more advantageous offer, the contracting officer should not use this method of testing the market.
(2) An informal analysis of prices or an examination of the market indicates that the option price is better than prices available in the market or that the option is the more advantageous offer.
(3) The time between the award of the contract containing the option and the exercise of the option is so short that it indicates the option price is the lowest price obtainable or the more advantageous offer. The contracting officer shall take into consideration such factors as market stability and comparison of the time since award with the usual duration of contracts for such supplies or services.
(e) The determination of other factors under paragraph (c)(3) of this section—
(1) Should take into account the Government's need for continuity of operations and potential costs of disrupting operations; and
(2) May consider the effect on small business.
(f) Before exercising an option, the contracting officer shall make a written determination for the contract file that exercise is in accordance with the terms of the option, the requirements of this section, and Part 6. To satisfy requirements of Part 6 regarding full and open competition, the option must have been evaluated as part of the initial competition and be exercisable at an amount specified in or reasonably determinable from the terms of the basic contract, e.g. --
(1) A specific dollar amount;
(2) An amount to be determined by applying provisions (or a formula) provided in the basic contract, but not including renegotiation of the price for work in a fixed-price type contract;
(3) In the case of a cost-type contract, if --
(i) The option contains a fixed or maximum fee; or
(ii) The fixed or maximum fee amount is determinable by applying a formula contained in the basic contract (but see 16.102(c));
(4) A specific price that is subject to an economic price adjustment provision; or
(5) A specific price that is subject to change as the result of changes to prevailing labor rates provided by the Secretary of Labor.
(g) The contract modification or other written document which notifies the contractor of the exercise of the option shall cite the option clause as authority.
Also reference DFARS 217.207
217.207 Exercise of options.
(c) In addition to the requirements at FAR 17.207(c), exercise an option only after determining that the contractor’s record in the Central Contractor Registration database is active and the contractor’s Data Universal Numbering System (DUNS) number, Commercial and Government Entity (CAGE) code, name, and physical address are accurately reflected in the contract document.
See PGI 217.207 for the requirement to perform cost and price analysis of spare parts prior to exercising any option for firm-fixed-price contracts containing spare parts.
Included at https://acc.dau.mil/CommunityBrowser.aspx?id=518384 is a template you can format and use for your D&F.