G'day Ray,
When your K5 first arrives, I'd suggest a little jig.
Then:
Check it's in good nick, if it is, charge the battery. Read the instructions whilst the battery is charging.
Once the battery is charged put an SD card in, format it and confirm if it has the most up to date K5 firmware. If not download and install the latest firmware. Set your camera up to your preferences (RAW/JPEG, DNG/PEF, and camera settings).
Once this is done go out and take photos. If you find there are issues with images being out of focus check for front/back focus. If it is out you can find the steps for testing and adjusting for back/front focus in the forums. Don't forget to ask if you can't find things here, most people here are very happy to assist.
Other than that, you should be good to just go out and explore what you can create with the K5. The only other things you
may consider is If you use lots of manual focus fast lenses you
may want to swap the focus screen. The second thing is if you find the body small in the hand (the pinky finger seems to drop off the bottom of the grip for example) you might want to add a battery grip. I have used grips on my K10D, K7 and K5, I personally feel it is better balanced with one. Not an essential of course, but something you can do with this camera if it suits you.
f the camera has been looked after then you probably just need to charge the battery and format a card to be on your way. The K5 is a great camera, I still use one and expect you will find the extra control it gives you will mean plenty of years to enjoy what you and your new camera can create.
Tas