I would recommend that you also watch a lot of muay thai matches and study their technique.
But having an instructor is so much better. Best is having instructor and watching lots of instruction vids as well as stand up fighting.
For kicking I recommend watching all of Buakaw Por Pramuk's matches (in K-1 world max).
Your friend will probably be able to help you in the beginning with the basics, but without an instructor there will probably be a lot of things that you could improve that neither you nor your friend notice.