f the exterior needs cleaning, just use a good cleaner like Fantastic or the like - note though that Fantastic might actually remove some of the stamped on text and logos if they are painted on. Be sure not to get any in the machine itself.
If the interior needs cleaning, you can either use a commercial espresso machine cleaner or us vinegar and water to decalcify the inside.
To decalcify using vinegar add 3 oz. of vinegar to 20 oz. of water, and let it run through the machine. Then run about 3-4 times the amount of fresh water.
If you can disassemble the frothing wand, do so - and get the wand clean. If little rubber gaskets pop out, DON'T LOSE THEM and remember what order they go back on.
The same thing goes for the brewhead, that's where the water comes out, most pump machines have a brewhead that can be removed with a single screw - tilt your machine on its side (make sure there's no water in it) and disassemble that part. Use toothbrushes, use a clean j-cloth, whatever it takes to get all the nooks and crannies.
Once the machine is cleaned inside and out, run one more full batch of water through it, making sure you stop the pump just before all the water drains out.