Pun intended (I bet that joke's been done to death)...

Anyways, I've got a 2.8 V6 with, what my dad believes, is a baffle gone bad. The engine gives out a grinding noise when in drive and moving, and when in park, there's a light knocking noise.

I'm just wondering how much it's gonna cost, how much work is involved, and how serious is it? I drive about 60 miles a day at an average of 55mph.

Thanks!