"I am eating a turnip, I am so happy."
Translation:Tha mi ag ithe snèap, tha mi cho toilichte.
Glè mhath. To be fussy, it is le ìm. Le only changes to leis before the article or certain other words.
Also, there has been a argument about whether a plural of snèap even exists. It is usually means 'turnips' in general, rather than 'a single turnip', so you should just say snèap for 'turnips'. Their translation is poor. It should be 'I am eating turnip' or 'I am eating turnips'. So saying 'I am eating a turnip is weird, as they are usually well beyond being counted by the time they arrive on your plate with the ìm. In fact, a decent-sized turnip is too big for a meal for one.
Thanks! ... so: nas fheàrr ag ràdh: leis an t-ìm math (... ach ... 's fheàrr sneap gun ìm na a bhith gun sneap. Haha). So true the bit about plurals and uncountables which is a perrenial translation problem since there's often little internal logic, especially in spoken language: "I am going to cook (these turnips/this turnip/turnips) and then you can eat (some turnip /turnips/turnip). ... after you get the sheep into the barn". ;-)
There's always more to catch you out: Tha snèap leis an ìm math. Nouns behave a bit differently after prepositions.
But the important thing, as you say, is to have the snèap, with or without the ìm.
If you are confused about the logic of singular and plural, you really should try Welsh.