300E O2 Sensor Replacement

Hello everyone.....My neighbors mb/bmw mechanic made a service call nextstore and told me I have to have the O2 Sensor and a catalytic converter hooked up so the car will run without a computetr glitch. After
talking to him I looked at the metal end of the 02 sensor and learned that the metal was a beat up and bend a little. I saw that there is a rubber insulation piece that guides the wires through inside somewhere. MY QUESTION- Is there a way to get to the other end from the inside of the car? Is it a hard job? Is 300 dollars a good price for an aftermarket CAT? Whats the difference between one CAT and an aftermarket cat? Thank you all- Charlie- Monmouth County NJ
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
NVM, I figured it out...
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Motorsforum.com is a website by car enthusiasts for car enthusiasts. It is not affiliated with any of the car or spare part manufacturers or car dealers discussed here. All logos and trade names are the property of their respective owners.