You would be compounding a problem. The best thing to do is remove the old weed barrier fabric and mulch and replace with new. It is kind of like putting a new roof over old shake shingles or not "prepping" before painting - it creates more work and headaches down the road. Yes, more work up front, but much less work later.

Thanks for the input.
I figured that but was hoping it may have some benefit.
Guess I know what my sunday chores include.

Why do you want to take out the old fabric? Is it not working? If it is still usable maybe shovel off the bark and then put the rock over it.

If you cover your yard with rock you may end up doing a lot of picking of litter out of rocks. It depends on your situation (what sources of litter there may be) and aesthetic requirements.

Here is a link that might be useful: Landscape Cloth PDF