So I've pretty much never dated anyone unless you count a fake 2-year relationship with a girl in high school.  It was an inside joke between us since no one else seemed to notice that we never did anything that couples do (including going on dates).  

Anyways, my best friend is now considering setting me up with someone.  I'm hesitant because I know nothing about dating or relationships.  I know nothing about the guy he's planning to set me up with except that my friend thinks we'll get along.  

Besides the general 'no past experience' fear, I also feel like I might be risking my friendship.  Since my friend is setting me up with his friend, if it doesn't work out then our friendship could be affected.  

I'm not sure if I'm mentally ready for a relationship right now either.  I'm not seeking out a relationship, so the only real motivation I have is curiosity.  That alone doesn't seem like enough for me to say "Let's try it."  

Given that I have nothing to go on, I'm just looking for any useful advice people might have.  I put a very thorough amount of thinking into literally everything that happens in my life, but I don't know where to start with something like this since I have nothing to relate it to that I can think of.  

Well, if you're not mentally ready, just tell your friend that you're just not ready, and contact his/her other friend, and ask to be friends with you too, and that way, if you guys truly do have a connection with each other, who knows, love could blossom. =)

My advice? Follow your gut. If it says no, or is hesitant, you have reason to be hesitant. There's a saying;

Pig or cow? 

I don't think that if you do not end up good with your friend's friend, that it's going to effect your relationship with your friend.

Well, you can give it a try, but make sure to make clear your intentions of not being in a relationship to the other person too. Because, otherwise he might start "planing" things for you 2 in the future. So just let him know that you want to give it a try and if it works, it's fine, if not you can try to be friends.
That's what I would have done if I were you.

IF you feel you're not ready, then you should just say you aren't, and take all the time needed until you are ready. That way, you're prepared and more comfortable doing so.