Yes, it's worth having a professional do it.
While the right archival materials are available, they aren't cheap, and you only need a very small amount of each. So doing it right will be expensive.
You can also run into problems that are daily things for a pro, but a huge puzzle for the rest of us.
For instance, I think it's likely the tear was caused by the adhesive used in framing expanding and putting pressure on an already weak crease.
So the first problem is what exactly is that adhesive and how do you remove it without doing more damage to the paper or autograph.
After that, you need to know how to neutralize whatever you did to get the adhesive off.
After that it gets easy, a good archival paste, and mulberry paper.
I do my own preservation work, but my stuff is cheap enough that the right materials cost more than the items, so I use "next best" type stuff.
I would not work on this if it were mine, I'd send it to a pro.
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