Is there any major issues/ problems that I need to be aware of, tried to Google and can't find much info on the specific on the 323i's, lots of info on other 3 series though.
If I'm not mistaken the 323i uses the same engine as the 325i, just slightly detuned. I may be wrong. If that's the case, just research under the E90 325i and you should get your answers.
Water Pump: seems to be a weak point in all e90's
Diff: diff is another weak point.
Oil filter housing gasket and heat exchange gasket: These rubber gaskets get brittle over time.