Hi nanag and Jennifer
The shipping one is pretty easy, once you know how ;-)
First you need to set up a profile,
THEN you can apply the profile to multiple items with the "Apply Shipping Profiles to multiple listings" option at the bottom of the Shipping Profiles page - for more info
http://www.etsy.com/help/article/190This only really works if the shipping is the same across lots of items, wouldn't be so useful for vintage or where each item will need different postage prices.
Not sure about changing the cost of multiple items in your shop...