Thank you all for the feedback.
The photo is 21" x 8", so it is pretty big.
I generally like things to be original but think the smudges really detract from it and I worry that whatever that substance is will not be good for the photo or the autographs going forward. Beyond that I would stabilize it and leave the rest of the condition as it is - I like that it shows that it was owned by a kid on the team. I am a bit on the fence about even leaving the dirt for that same reason but just can't decide which is the correct way to go. If I find out that it will be $1200 to have it cleaned that will big a big factor too