Well if you can find a way to grind them up, you could use the pieces as a mulch. I don't know what else to suggest here. Check with your town about a recycling program. Many cities pick up organic waste and compost it. You could certainly put the leaves in your own compost pile, but the branches will be more problematic unless you chip/shred them. As for replacement trees, I need to know more about your site to recommend anything. You can go to our Plant Encyclopedia on this website and do an Advanced Search to see what it tells you, but you'll need to fill in the criteria: sun/shade, soil conditions, etc before it can help.