yes you can change it only diffenrence would be the engine supports. Plus you need to find a mitsubishi engine that has the driver side all the betls. In the older engines its all in the passenger side.
My opinion its still better to have your 1.5 overhauled at least you know that everything inside is new. I had owned both the lancer GL and GLXi both have almost the same fuel consumption but the GLXi uses a bit more.