Hi Tatiana,
I live in Ireland, moved here from Germany over 4 years ago. I already had my driving licence so I could just start driving. It really isn't hard at all, honest.
I would suggest driving a car with the steering on the right unless you bring your own one from the continent anyway. But the steering wheel on the right just gives you the same perspective that all the other drivers have and you will feel safer sooner.
First time I was driving on the left side was actually much longer ago and it was a rental car while on holidays - it took me about half a day to get used to it but that was it! My boyfriend at the time had trouble getting me out of the car, I enjoyed driving "on the other side" of the road that much!
I'm sure you'll get the hang of it very quickly!