"He is the engineer."
Translation:Is é an t-innealtóir é.
You do need it, actually. Unless you're speaking Ulster Irish. You can drop them both, however, and use eisean.
http://www.nualeargais.ie/gnag/kopul5.htm#bestimmtes Prädikat (ctrl-f "He is the" for the relevant section).
So you can have:
Is é an t-innealtóir é (Standard) Is é an t-innealtóir (Ulster Irish only) Is eisean an t-innealtóir (Perhaps more colloquial, emphasis form)
No. The first é in Is é an t-innealtóir é is a sub-predicate that is required to separate the copula is from the positive predicate (an t-innealtóir), and the é is at the end (the subject).
With a 1st or 2nd person pronoun as the subject, the subject actually comes first - Is mé an t-innealtóir - "I am the engineer". When the 1st/2nd person pronoun is the predicate, you use the emphatic form - Is mise an t-innealtóir - "I am the engineer.
To say "I am the engineer, with the emphasis on "the engineer", you say Is mé an t-innealtóir*
I still have no idea what you mean when you talk about this "copula" and I'm very well educated... I thought. I have no clue what the copula is and when to know it's involved or why it matters. I'm beyond frustrated, thinking there's no hope for me with Irish. Physics is easier than Irish!