question should, can it be done in a safe way?
Yes, but can you?
There are a few demo videos, if you do a related search, but still a risk of bringing more dust, scratching the mirror, etc.
Take it to a good reputable local camera store, and ask about the costs. More often, they might give you a labor discount, if you buy from them, aside of having some sort of warranty on services and parts.
It's done often, and I have done it on my 40D with success. However, I won't do it again, and for sure not on the 5D2 myself.