Take little steps. First thing's first, figure out how to program and power up the 8031, possibly blinking a few LED just to show that you've actually got it working, then look at the GSM units datasheet and figure out how it communicates, then figure out how to write the code to get the 8031 to talk to the GSM unit until you can succesfully broadcast messages with it. Then go on to interfacing to the 3-phase metering IC and figure otu it's requirements.. It's pretty simple if you just take it one step at a time. IF you look at the whole project it may seem intimidating, which is why you break it down into simple steps, verify that things are working properly at each step before you go on or there's no way you can figure out what's not working when things go wrong. You can't just plug the whole thing together without testing and expect it to work.