5k training
Personally I find no difference between running clothed and running naked, so as far as training I would say you just need to get out there and run some miles.
How long before the run, and how much were you running before you stopped in 2008?
It took me a full month to "wake up" my body after a year long pause in running, but for a ten year hiatus you probably should train like you are a novice runner, at least at first until you know your body is ready to a faster regimen. And, if you read on some website that you can train to run a 5K in only 2 weeks... well, yeah, you can have your body ready to cover a 5K distance faster than it will do it today, but you certainly won't be able to get back to your 2008 times in two weeks (probably will take more like 10 weeks). Not trying to discourage, just don't want you to hurt yourself trying something unfeasible. Good luck and have fun with the run. It's great to be able to run naked.
Following an app or an article from a book, etc is OK. Just remember to listen to your body. If you think you need more time to advance to the next step take your time. It's far better, and healthier, to take your time and get to the 5K slowly, than push yourself and potentially injure yourself. There is nothing like sustaining an injury when you first start a physical activity. It can really dilute your motivation. As Goofy, from one of the Walt Disney cartoons said, "Slow and steady wins the race". And if you're just starting out this is really good advice.
I had already run a couple of 5Ks before my first nude one last summer. I beat my best time by almost 2 minutes while running nude! And it was a pretty hilly course (Sunny Rest in PA). It really is more fun running nude. My only clothed 5K this summer was off on the pace and I couldn't do the nude race, so I want to see if next year shows the same increased performance running nude.
For me I sunscreen - all over! I have skin that definitely requires protection!
More importantly, I've seen some damage on others and had experienced some underarm chaffing wearing a singlet running distances when younger. I used it for both my 5k road and 7k trail nude runs - body glide!
Outside of that, it's fantastic running naked! Cooler, lighter, exhilarating....the running part - if you've trained for it, you're ready!