spiders/insects getting into 5th wheel, common?

Spiders happen. :) I'm sure you've found them in your home, too. Remembers one pregnant spider will give you hundreds of little ones but not all will survive, thankfully. They do grab some of those night bugs so they're not all bad. Just keep squishing and you might get a handle on it unless you're overrun with them. Personally, I wouldn't start spraying inside. Chemicals are worse than spiders. Good luck!