Talking about age.
Is this how you say, "I am only thirty years old."?

Nílim ach tríocha bliain d’aois

And is "I am only thirty seven years old."

"Nílim ach seacht mbliana is tríocha d'aois."

in Irish?

Question

Talking about age.
Is this how you say, "I am only thirty years old."?

Nílim ach tríocha bliain d’aois

And is "I am only thirty seven years old."

"Nílim ach seacht mbliana is tríocha d'aois."

in Irish?

Answer

They're both correct. 
You could also say: "Níl mé ach deich mbliana ar fhichid/is fiche d'aois" and "Níl mé ach seacht mbliana déag ar fhichid/is fiche d'aois", using the old vigesimal counting system.