I got a 2000 Grand Cherokee Laredo 4x4 and want to change the o2 sensors and would like to know which ones are the best ones to buy for the jeep and what the part number would be. I want to change all of them so how many are they too and shuld be on the exhuast right? Thanks

Are they all bad?
Brand: Common wisdom is to replace them with Chrysler OEM.
How many: California emissions vehicles have 4, two before the catalytic converter, 2 after. Federal emissions vehicles have 2, one before & one after the cat.
The part numbers vary (European export or domestic) depending on the location, before the cat or after, and the length of the pigtail:

56041676AA
56041212AE
56041344AD
56041212AF

\I would go with BOSCH

BOSCH is a better brand, and its a real good OEM part.

But i went with Denso and my truck dosent run at top performance.
I was short on money then, whenever i can im going to put BOSCH sensors on. I work at Advance Auto Parts and thats what everyone buys.

i would just stay away from Denso.