Love your enthusiasm but...
Linux is far from virus free. Just do a google search on rootkits for linux. Or the newest usb-virus problem.
Sure the community will hack it out, but try not to mislead on accident.

Any OS has got a vulnerability list a mile long, it's just a matter of popularity.
Also, don't confuse your Ubuntu machine with all the other flavors of linux. When you feel more comfortable spread your wings and try other distros. Don't even let yourself be confined to Debian only flavors! Hell, for a new user to Linux I actually rarely suggest ubuntu (SO MUCH BLOAT) instead I offer them LinuxMint, it's ubuntu if MS or Apple made Debian. hehe
Another note is that there's differences in free. Free as in Beer and Free as in Speech. Not all licenses are as in Beer.
Anyway, it's nice to see your enthusiasm and your guides there.

Have fun and enjoy a safer more stable OS.
-Shoe