Isn't the newbie silly

Only kidding mate, serious answers to follow
1) Almost certainly YES.
Leather (or Kevlar) is the best thing to be wearing if you end up on your butt sliding down the road. Jeans are just about passable round town (I should know, I've been on the deck 4 times in my younger years and got the holey jeans to prove it) At no more than 20 mph they at least offer you more protection than the burbury shell suits the local spotty yoofs wear on their sh1t box scotters.
If you're mainly commuting then the textile jackets & trousers can be nearly as good, with kevlar & body armour on the impact areas with the benefit of being waterproof/warm and cool as required
2) Under leathers? No. Just my lucky biker pants and a polo neck
Under cordura etc stuff? Depends. It is designed so that you can have your work suit on underneath and just strip off like superman when you get to work (no phone box required


Hope this helps
Ben