Check engine codes diagnosis

[DeNoZZo]

I went to autozone earlier today and got my check engine light scanned. Here are the codes they gave me- P0403, P0136, P0141, P0443, P0115, and P0135. In the description on the print outs they gave me, it shows that a few of the codes are emissions related, and I know that stuff has been removed on my car so I'm not worried about that. But the other codes are 02 sensor related. From what I understand, the rear o2 sensor does nothing, right? But I plan on replacing the front sensor.

My questions are-
If anyone knows how to decifer the codes, can you tell me what is wrong and what should be fixed?
If I do replace the front o2 sensor, should I replace it with a wideband?
What is a wideband, and what advantages will it give me?
Is a replacement o2 sensor hard to install?


Thanks!