Is the 30 teeth chainring on Campagnolo Mirage 52/42/30 crankset replaceable? I have new (for me) 2008 Orbea Onix TDi with existing 50/34 front crankset.
My shifter is 3 steps - to switch from 1st to 2nd I have to click twice.
All parts are Campagnolo Mirage.

Climbing the hills on it for me is too hard - I'm 230lbs. I've just ordered a new 52/42/30 Campagnolo Mirage crankset. But I have a feeling that 30 teeth still won't be enough.

Can I replace the 30 tooth chainring with let's say 26 to make climbing easier?
And if yes, which one would you recommend?

Thank you.
The bolt circle diameter for recent road triples is 74 mm, which allows something around 23 teeth. Looking at the catalog of Specialites TA, their smallest chainring is 24 teeth.

In addition to triple crank, you will need a triple compatible front derailleur and very probably a long cage rear derailleur. There are multiple discussions about chain capacity on this site, search for them.