Hi,
I have some knowledge of Salesforce, from the perspective of other users. My understanding is that it does take quite a bit of customization. I'd suggest going to Salesforce and getting some help in setting it up.
As a rule of thumb, I think using your single piece of software is better than getting another piece of software to do part of the job. One way or another, you are going to have a learning curve, and better to invest it in a product that you are already using and have support for, rather than starting from ground zero again.
I do think it's a good idea to keep your volunteer management integrated with your donor management.
Best wishes,
Sasha