Aircraft in hangar for scheduled maintenance for 3 days.
Replace the orings, is base maintenance let the operators know of the delay immediately you find the parts not available.
If you are going to cut any corners it needs to be plausibly deniable in the event of a stuff up.
If you mean to lie about doing it, then that is a reason not to do it.
Only do what you can justify amongst your peers, and in a court of law.
Contact my engineering department and ask them to issue an Engineering Approval for the proposed deviation from approved data.
Hmmm, sounds like an experienced LAE has used his experience to decide to work outside the manual and has advised Quality department to rubber stamp his advice.