Yes you can still change the oil on your BMW by yourself.
As for the computer reset light, it's basically a timer that tells you when to change your oil. I think the interval is around 5000 miles, when you're closer to the mileage, there is a little oil change light in the instrument cluster that will change from green to yellow and finally to red. What the reset tool basically does is tell the computer that the oil has just been changed. So, you don't really need to reset it. (provided you can live with the light on the red mark, which is not a big deal, it's a small light)
or
you can buy the reset tool for $40, or make your own using parts from radio shack for <$5.
In addition to this, there are also lights for service intervals (every 15,000 miles, change filters and stuff). Same thing. You can just ignore the light and the car will run just fine. Although a lot of private mechanics that works on BMWs have this tool. ($40 is nothing compared to snap-ons) If they don't have the tool, you probably won't want them to work on your BMW anyway.
I'm not sure about the position of the oil filter on the 318, which is a 4 cylinder. If she's buying the 6 cylinder models (323, 325, 328, 330), the oil filter is very easy to find. Open the hood and the first thing you'll see is the oil filter. BMWs have a good reputation of being an easy car to work on.
As for Hondas, that I don't know.