No it's not hard at all. As a matter of fact it's very easy "on the technical level".
However, Nvidia decided not to support their products on x79 platforms running in PCIE 3.0
Don't know about other companies where they stand but, I have tested a raid card & it ran in PCIE Gen 2 while it's Gen 3.
Do some research about that thing whether you'll need it or not and, then see if it's good to be said or not.