viesmann vr1-27 w/ Riello 40 F3 startup issues?

Last nite burner failed to ignite.
Back on 12/11 we lost power for 5 days.
Not sure if burner was running when power went out.
But when power came back on, 12/16, the Red light/button had to be pushed on the Riello to get it to start.
All was OK until last nite, 12/26.
Actually in hindsight, I have noticed burner seemed to run too long and light smell of oil.

Whole unit was installed in spring of 2006 and has not had any service since!

I suspect a dirty oil filter and/or a dirty nozzle.

I am going to change the oil filter,

How do I clean or change the nozzle?

tks