I recomend freezing/thawing the fruit before adding it to primary (use a nylon fruit bag for easy removal). This helps break down the cell walls of the fruit and let the most amount of juice flow into the wort. I don't use campden tablets, so I just pour boiling water over the fruit- if you're worried about pectin, use pectic enzyme- I have never had a pectin haze in a mead before. As far as amounts of fruit to use, it really depends on what you want to achieve in the finished product. If you want to bring out the honey character and just have a hint of fruit use 1-3lbs, but again this varies. If you want lots of fruit character, use way more than you think you would. My last mead was a raspberry melomel and I used 15lbs of frozen raspberries in there! Some would say that this is way to much, but it really did turn out fantastic. Spices are not an uncommon addition to mead (check out some metheglin recipes). I had a blueberry metheglin that was yummy- had cinnamon stick, whole cloves, slices of ginger, and lemon peel. Here is a link to Got Mead's recipe links: http://www.gotmead.com/mead-recipes/
Good starting point for doing some recipe research.