Irish meat

Am hosting a gourmet dinner in a few weeks and went to buy the meat today. Got talked into buying Irish beef by a very cute, and sadly very young, shop assistant. But he seemed to know what he was talking about, and that's good enough for me...hehe. So I bought 2 kg's of beef that I have to fry for 5 mins, then stick in the oven for 3-4 hours in 80°. This is a first for me, so I'm really, really hoping that it'll turn out allright.