Scanning negatives, printing photos and website pictures

[Egomonster]

I should send part of my B & W photos to be printed for an exhibition (size will be about A3), part of them to be printed for a brochure and part of them to be dipslayed on a website. However I'm not sure about the picture quality etc. because I've never printed photos before, and I won't be able to see the result before the exhibition cause it will be abroad, so I'd appreciate some advice here... (Can't even ask the person who will receive my photos because he's hiking on mountains...)

I have a few questions, would someone be able to answer them...?:

1. How good a negative scanner should I have? My own scanner is only 1800 dpi, surely that's not enough?

2. As which format should I save the pictures? TIFF for the ones to be printed and JPEG for the ones to be displayed on the website? Which resolution, and what about the color bits? (My pictures are black and white.)

3. What would be the maximum image size so that it could be handled and printed etc. on a home computer? (Sending it is not a problem because I will upload it on the receivers FTP...)

Thanks in advance for possible answers!