I don't think it is weird to let someone know that you appreciate the impact they have had on your life. I think that is wonderful.

Having said that, I think the real and pressing issue is that you are feeling a need to talk to someone about what's going on in your life right now.

So I would say do both. Send a letter and find someone to talk to about what you're experiencing now.

I think your wanting to reconnect with him by letter is a way of saying to yourself that you'd like to have him or someone like him available to you now like he was then, that you are feeling a familiar pain and so you are thinking of a familiar way to get help with that pain.

Does that sound right to you?