I personally don't think it would be worth it to buy a new 1155 motherboard for your system. The current standard is 1150 and 1151 drops in the second quarter of this year. If you can find a relatively cheap one on ebay from a well reviewed seller then go for it, otherwise I would not upgrade unless you have to. And you may have to. You are pulling your current motherboard and processor from a prebuilt lenovo, prebuilts often (but not always) use a BTX format motherboard instead of an ATX, so your new motherboard may not fit in a new case, at which point it would be worth it to buy a new board because the 3770 is still a great processor.
Also for your cooler you can get the Cooler Master TX3 for less than $20. It works great for stock clock processors and is not as large and bulky as the Cooler Master Evo and also easier to install.