Originally Answered: Which language should I learn? (Excl. German/Spanish)?
Your friend is quite correct. Norwegian and Swedish are very similar. Some claim that were it not for the fact that each is a national language (but see below) they would be considered different dialects, not languages. Actually the languages of Scandinavia (that is, Danish, Swedish, Norwegian, Icelandic, and Faroese) are all North Germanic languages, so related, and perhaps a common parent language about 1000 years ago. (Finnish is quite different, and not even Indo-European.)
Here is a major difference: Norwegian was influenced by Danish for 400 years, when Norway was a Danish province, and all culture, economy, education, church business was conducted in Danish. Thanks to a weakened Norway -- the Black Death decimated more than 50% of the country-- the written language in Norway pretty much disappeared. Swedish has had a continuous development.
Swedish has a few more conservative (in linguistic terms) traits .. for example it has more indefinite noun plural forms (-ar, -er, -or) endings, while Norwegian (like Danish) has basically -er. Same for verb past tenses.
Pronunciation is quite similar, although standard Norwegian shows more diphthongs.
One other answer points out that Norwegian has two standard written forms: bokmål (more Dano-Norwegian) and nynorsk (based on the western dialects, less influenced by Danish).
As to where or how to learn them, you can go to the database my Univ of Minnesota maintains about where you can study about 300 less commonly taught languages (all but French, German, Spanish, and English) in North America (see first link below).
I am a Norwegian teacher and have my own website (2nd web site below) with a number of pointers to studying Norwegian on your own, including some old email lessons I sent out many years ago.