Mmm thanks, something like these? Amazon.com : Alpine SPR-10TW 1-inch Silk Ring Dome Car Audio Component Tweeters (Pair) : Vehicle Tweeters : Car ElectronicsI put alpine tweeters in place of mine in my 06. I had to make adapter from a little sheet metal and factory clips. Came out great they were WAY better than factory. Cheap too as I remember I don't think they were expensive, but as with anything you skies the limit on price.
If the price is right on Amazon I wouldn't worry too much about warranty. I have always found alpine to be pretty reliable. Every pair of their speakers I have had out lasted the vehicle. I don't know if you will need the crossover. Mine did not come with one, but I think there is a factory one. There may have been one built into my tweeters though.