Darla- release forms are relevant to where you are based. if you plan on finishing your film in NJ, then a US form is fine, you don't need any Italian changes because the legal stuff will all be in the US. HOWEVER, jumping back to your sound issues(!), when traveling to foreign countries, you cannot take a wireless mic from the US. hopefully, your DP has sound gear that is adjusted to Italian broadcast specs.
as far as gear and especailly in regards to shotgun mics, i'd say, depending on how much you want to spend, get a Sennheiser ME-66 for $250 or a Sennheiser MK-416 for $1,200. the 66 is really good for the money, the 416 is really, really great, but costs.
as to how to use them, sometime i am the interviewer as well as the soundperson. for these situations, i use a hand unit which is basically a pistol grip with foam for the hand and a shock mount on the top for the mic. i can then, very easily deal with interviewing AND doing good sound. obviously, this doesn't work if one is running around a lot, but even then, if you stay close by the subject, it works fine.
i would try to avoid, at least in the beginning stages of your doc making, doing both boom and interviewing. that's hard. i've done it and it's tough. but if you have to, don't do mixing while you're at it, just do the boom and the questioning.
most DP's are adept at riding levels so unless you have more than 2 people or a big crowd scene to film, you, as the sound person, shouldn't need to deal with mixing the sound before it gets to the camera.