For oil I use Mobile 1 synthetic, with ac Delco filter. Just stay away from Fram as their quality has gone way downhill in the last few years.
For visual mods checkout PFYC.com. Their is also a SE front lip from GM that is pricey but looks the best IMO. You can swap the GP GXP spoiler for the stock one if you want. Thats all I can think of off the top of my head!