Question: A friend who you've known for awhile has a crush on you, and you found out through a close friend that you both know!
So do you:
A) Approach him and take the next step??
B) Do nothing cause you would rather not ruin the many years of friendship if the relationship goes bad??
Seems like a tricky question that can't be answered with a simple "a or b" answer. We'd have to know more about you both before giving any advice.
What are your feelings towards the guy?
What's your history with the guy?
What are both of your personalities like?
Do you have good chemistry between each other, or do you feel you have an uneven flow?
How have you dealt with disagreements in the past? How major/minor have these disagreements been?
How do each of you behave under pressure?
How secretive/honest are you with each other?
How do you deal with borders/personal space?
What are your aspirations, goals, general world view, beliefs? Are you both compatible or do you have a lot of differences?
I mean, these are only a handful of questions that can be asked to, honestly, anyone seeking a relationship. You don't have to answer these questions publicly, even. Just think them through and answer to yourself. And don't rush. Really, really think it through.
In the end we can only give you advice, dude!