Exhaust manifold

Am told I have a 2 bad catalytic converter (one on manifold, one on tailpipe). One dealership says need to change both out, one says change manifold out with headers and the tailpipe with aftermarket brand. First option $2400, 2nd less than $700. Questions I can't get answered is what to do about o2 sensors on both sides.  So I ask, has anyone converted to headers and did it work?  '01 Suzuki Grand Vitara 2.5L