1. Generally whole backpack trades are represented by the putting the untradable badge (mercenary, ect) on the have side and keys / buds on the want side. You would also put in the trade notes that you are selling your backpack for pure only. There are also a few users on OP that buy backpacks for PayPal.

2. Do not click on any links sent to you either in steam chat or on your trades, and always make sure when entering your credentials that it is the actual steam site.

3. You will need a substantial amount of rep before you can do PayPal trades, if not you will most likely be required to 'go first' meaning you will give the buyer the keys and then they will send the money to you, you can also use a middleman.

4. Check their steamrep for any scammer tags or alts, check their steam profile and see how old their account is (generally 2 years+ is ok.) and check for any previous trade bans. Using a trusted middleman will remove most of the risk when making a PayPal trade (always use a middleman that you know is trusted).

5. This depends on how quickly you want to sell them. A cheaper price will get you a faster trade, but less money, while a more expensive trade might take longer for someone to buy. Do some searches on the site and see what others are selling for and base your price on that.

Thanks for the good answer!