I have the 1.6 rockers installed on my car. They are relatively easy to install. You just have to be careful with the lash adjustment. Plenty of room to install them and the stock parts are adequet for them. I would recommend replacing the hydrolic lifters when you replace the rocker arms since it will be easy to replace them.
As to the power, you will feel the power increase immediately. About 10% more across the entire rpm range.