You can go the travel agent route or book everything yourself. Cheap ones to attend is Australia, Malaysia and Abu Dhabi. The classics like Monza, Spa, Silverstone tend to be more on the expensive side.
Best seats are anywhere opposite the pit building or in the overtaking spots (e.g. into Turn 1) which makes photo opportunities great as well. Grand stand (preferably closed) are the best, unless your friend is the walk about type. Some venues allow walk about tickets that give general access to all areas of the track except for grand stands. With grandstands though, seating is reserved.
Organisers usually include a free pit lane walk on the Thursday if you buy 3-day tickets. Hospitality tickets include pit lane walks as well and provide your basic food and beverage at the track and there's usually a reserved seat included as well.
Have a look at the hotels around, say 5-10km radius from the track if you want to save a bit on the accommodation. Remember the teams book out entire hotels close to the track and as with all hotels, the prices go up around that weekend. Look at the public transport available as well. SOme packages include transfers to the track but not all days.
All inclusive packages appear cheap but look carefully at the tickets you're getting. Usually the cheapest with limited views or something like that. You are allowed to choose different types of tickets but that just adds to the cost of the package. Be careful of some site that also look cheap but they're just tickets and accommodation and excludes flights.
Most of the tickets that you buy come with earplugs and all that jazz. The program you have to buy at the track.
Italy would be the best one to attend. The craziness of the fans is epic to witness and the track invasion is something to behold.
Maybe this will help with your decision making
http://f1destinations.com/
Some great information from people who've attended races
Take a big SA flag with and enjoy it