How To Replace Of Oxygen Sensor

I have 97 grand caravan 3.3L engine. I need to know the location of the bank 1 (upper) oxygen sensor. I cannot see it. Also, I need to know the easy way to replace the spark plugs located close to the firewall. Thanks.

I have a 96GC with the 3.8 ltr. The upstream sensor is on the top of the exhaust manifold on the back side of the engine. You're right, its in a tough spot and hard to find but, if you get under the van and follow the exhaust to the engine, the first thing you'll see is a small wire harness coming down from the engine. Follow this to the sensor. The sensor has three wires on it.
There's a few ways to change the plugs. Don't know if this is the easiest but, the one time I changed the rear plugs I loosened up the alternator and swung it down (I think) and was able to change the passenger side plug from there on the top side of the engine. I changed the middle and drivers side plugs reaching up from under the van. There is a pretty good size cavity where the exhaust and other crap runs through going to the back of the van. Reach through that cavity. It took me about 5-6 hours but thats because I removed the windshield wiper compartment trying to get at them from the top. It didn't do any good. Don't recall using any special tools beyond a standard socket set and plug removal socket. Please let us know how you did.