The only realistic translation would be from an existing, scholarly, publication. There is a Gaelic Bible to be found at http://www.electricscotland.com/hist...at/GAELICB.HTM but I cannot comment on the accuracy of it

From the above website your translation would read:

Mark 12:28
Is thainig fear de na Sgriobhaich, a chuala iad a consachadh, 'sa faicinn gur math a fhreagair e iad, dh' fharraid e dheth: ciod i a chiad fhainte dhiu uile.

Mark 12:29
Is fhreagair Iosa e: Gum b' i a chiad fhainte dhiu uile: Eisd, Israel: is aon Dia an Tighearna do Dhia :

Mark 12:30
Agus bheir thu gaol don Tighearna do Dhia le t-uile chridhe, agus le t-uile anam, agus le t-uile inntinn, agas le t-uile neart. Se so a chiad fhainte.

Mark 12:31
Agus tha an darna fainte coltach rithe : Bheir thu gaol dhad choimhearsnach mar dhut fhein. Nas mua na iad so chan eil fainte eile ann.