Can I transfer files from desktop to laptop and will music quality be compromised?

I'm going to shop for a laptop soon, and I'm doing some pre-purchase research. Two things I'm not clear on are: One, will I be able to connect my desktop to the new laptop to put my music library on it, and will there be a degradation in the sound quality. Two, whats the average monthly rate for wireless service. (Just general, everyday use)