Computer Question Regarding Wired Ethernet vs Wireless Connections

[Schneed10]

I love this site, you guys know stuff.

Quick couple of questions:

1) What's the difference in cost between a G adapter in the computer and an N adapter in the computer?

2) How easy is it to later upgrade from a G to an N (assuming I'm willing to also pay to upgrade the router to N)? Like, could a relatively smart person with limited computer knowledge and mediocre handyman skills get it done in a reasonable timeframe without damaging the computer?

Thanks for all the help guys.