David, what you want to do is possible, but depending on the construction of the amp it may be difficult. Many solid state amps have circuit board mounted jacks, making it difficult to replace.
Phantom power refers to the voltage through many XLR connected high impedance microphones needed to power internal circuitry (pre-amp). The SM58 is a low impedance microphone and can be plugged directly into most amps. Cables can be bought with an XLR connector at one and and a 1/4" plug on the other.
Like surf said, simple 1/8 to 1/4 adapters will work for the iPod. Or you could easily make a cable with a 1/8 plug on one end and a 1/4 on the other.