I thoroughly agree with those who recommended a thorough contract. Make sure you are covered in all unforseen circumstances. Make sure it clearly states your arrangement for the pictures. If she argues that you were doing "work for hire" type stuff then she could argue that all of the pictures are owned by her. If she is unwilling to sign or agree to anything ( assuming its fairly reasonable like all of this is ) then I would walk.
As for the fee, I am no pro, but then again, neither are you. So I wouldn't charge a crazy amount. The whole reason she responded to your ad is because she is looking for a low priced alternative. In a way you are buying experience by not charging her that much. If you DO need to rent equipment though, I would definately charge that to her, but again I wouldn't go too overboard. The package deal is a nice idea, but in this day and age, with scanners, make sure you don't have someone thats going to buy one package and then scan and print to their hearts content, then you aren't going to make much off those prints. So make sure you get a decent amount up front so that even if you don't sell many prints, its still worth your while.
I would just look at it like this ( and this is just personal ) and since its not really a PRO gig, because you are going into it as a "cheap amatuer alternative".
I make about $20 an hour at my day job not counting any overtime rates. So if it was 8-10 hours, I would say I would normally make about $200-225 at my day job. So if I asked for $300-$400, thats a pretty good days work for doing something that you kinda LIKE doing anyway. However, that doesn't account for editing time, but I would factor that into the cost of the prints. It also doesn't account for anything extra like if I needed to rent a tux or anything like that, or drive a long distance to the wedding, meet for a rehearsal, take engagement photos, etc etc.