now why would you want to do something like that?
its telling you that your cat is not functional anymore and basically that its clogging. the result is lost power, increased emissions, overheated exhaust and i do believe, but not sure, decreased gas mileage.
but if you must...
you can reset the computer by unplugging the battery for about 15 minutes...that'll tell you for sure if theres something wrong if it comes back
edit: yes, you should change your FIRST 02 sensor every 100k, the back one I don't know whether or not it should be changed, but my understanding is that is does not, and is only there to tell you if the catalyst is operating properly.
and just so you know...one of the best ways to clog a cat is to have a malfunctioning #1 o2 sensor. the rich exhaust fumes clog it up even faster.
looks like you've got two things on the list. but first, change that o2.
second edit: WHILE we're on the topic. you've had this car for 150k. since you haven't changed the o2....have you replaced your upper intake or lower intake manifold gaskets before? if you're burning coolant, thats another way you could murder a cat.