Changing your own oil is not that difficult if you have the right tools. Ramps (or jack + stands), a few hand tools, a catch pan, and something to hold the tray flap out of the way. Just make sure you are careful when re-installing the tray flap bolts - they are easy to cross-thread.

As per Jayhovah, you can get an after-market tray that makes things a little easier.

As per jchammond, while you have the tray partially unbolted would be a good time to remove the whole tray and do an inspection. For a DD, not really necessary at every change.

I wouldn't recommend installing a drain valve - just another place to spring a leak and the fitting/valve will cause some restriction during draining. Plus, you're going to have to mess with the tray to get to the valve, so it doesn't accomplish much. YMMV