You'll need a new motherboard (new socket 1155) and they take Dual Channel DDR3 RAM. The motherboards are much cheaper than the first socket 1366 boards. You can get a really decent motherboard for $150 to 0. There are several models to choose from. The 2500K i5 and 2600K i7 are the ones to get. They are around $225 and $330 respectively.
I'd go with the 2500K. It is only .1GHz slower than the 2600K and will overclock to about the same speed. 4.3GHz is what most people are getting them to with the stock cooler. 4.5GHz or 4.6GHz with a better cooler. The 2500K and 2600K are clock unlocked. This means you just have to increase some of the voltages and increase the CPU multiplier to overclock them. You don't have to mess with the base clock or make sure the other components don't get overclocked to far as you go along.
We'll be updating the Intel Core i3, i5 and i7 overclocking videos soon to show overclocking one of the new Core i5s and i7s. The videos as they are now are still very instructive so don't wait. The process is basically the same. Slowly raise the CPU frequency applying more voltage as needed to keep the system stable. The voltage settings didn't change so what is in the videos now still applies.
Here are some reviews of the new chips.