You've got "upgradeitis". It's highly likely that it'll cost you more to do all this than to just sell what you have and buy a new bike that is on sale due to all the parts that need replacing.

And other than the two additional gear teeth on the big cog what's it going to get you? If you want an easier bail out ratio just get a suitable 9 speed cassette. There's quite a few folks that feel that once we got up to around 8 to 9 speeds on the rear that it became more of a case of bragging rights when the 10's and higher came out. You can just pretend that you're one of us old curmudgeons....