Dia daiobh achan duine,

I was just trying to translate Larchfield Estate and wanted to check my attempt. It is the name of a wedding venue we have been invited to. I know there are lot of words for field not sure which is the most appropriate in the case. Not much good with the genitive case so the below may be way off.

Larchfield - Páirc learóige
Larchfield Estate - Eastát na páirce learóige

GRMA

Larchfield - Páirc na Learóige (as a proper name with article and capitalized initial letters)
Larchfield Estate - Eastát Pháirc na Learóige (no genitive form of páirc because learóg is already in genitive)

There are some places in Ireland called "Larchfield"
The Irish form there is Gort na Learóige

So Larchfield Estate - Eastát Ghort na Learóige

Go raibh maith agat a Labhrás.

All makes sense with the exception I am never sure when I should put the article in and when to leave it out. Are there any rules around this?

A place name should be definite.
So either a proper name is necessary (Seán's field = Gort Sheáin) or an article is necessary.

Neither field nor larch is a definite proper noun. So an article is necessary.
There are at least four possibilities:
An Gort Learóige = the field of a larch
Gort na Learóige = the field of the larch
An Gort Learóg = the field of larches
Gort na Learóg = the field of the larches