You will hear pros and cons for most systems. I have a wireless network with 3 PCs, one hardwired to the router and the others by USB adapters. My system is made up of netgear components and has been running for over a year without problems. I recently bought a cheap PCMIA card from novatech to fit into a laptop, which also happily works in the network.
If your present modem is of the USB type, you will not be able to connect a router to it. You will need to purchase a combined modem router that connects to your PC either wirelessly or through your ethernet port with a cable.