O2 sensor or EGR?

Hello, I was looking for some advice....I have a 2009 Octavia VRS diesel estate with 150000 miles on, I had some pop up codes when the engine light came on, they came up as 08448, throttle actuator and 08598, O2 sensor signal stuck rich, bank 1 sensor 1, on the fox well scanner.

I took it to kwikfit and after a 400 quid spend they replaced the throttle body and advised this would cure the other code....great i thought, however, 200 miles later and only 3 days the 08598 code is back, which even with my limited knowledge i thought would not be cured by the throttle body replacement.  As everyone does, i looked at the O2 sensor online and replacing etc...i did find someone that said 150000miles was about right for the sensor to give up the ghost.  I was wondering if anyone could advise on the following questions i have please?

1.  I assume that replacing the sensor will get rid of the fault but..is as easy as it looks on the you tube videos to do it yourself?  I assume again best to get a special socket off eBay to get it out as well?  Or, is this masking some underlying issue that the replacement of the sensor will only delay for awhile?  I think i can get a sensor and socket off of eBay for about 80 quid.

2.  Some say the egr and sensor are related, is it worth giving it clean with a cloth and does the egr valve spray cleaner actually work?  Is this also do able by a reasonably intelligent bloke with some diy skills but a novice mechanic...ie. can fill it up with oil and replace a light bulb in the car.

3.  Will an extreme cleaning additive do the job effectively rather than a take it off job?

4.  I do a 160 mile daily round trip commute, what do i risk damaging with this faulty sensor and the engine light on?

I suppose i am wondering whether this is worth the fix to only have something else go wrong down the line or do i get rid off now.

A bit more info that maybe of use....with the window open and when stopped at lights i think i can really smell the exhaust.

Thanks for the help, i love my car but the missus is in the get rid mentality before something else goes wrong....

Fruity