paypal is just a way to pay for stuff online using a credit card. if you wanna buy/sell stuff ya gotta use like ebay as for shipping prices there's probably some chart or something on ups' or fedex's website that tells you
If you have credit you can apply for a PayPal acct. and get a PayPal credit card also. There are many other options too. Then you can make purchases. If you're too dumb, as you say to understand about it and do your own research and read up about it then I recommend you do not get an account. It takes responsibility on your part to not be taken advantage of. Do you have on-line virus and spyware/malware protection? All of these things need to be considered for your own protection! Harsh but honest opinion.
If you want to send money, click that tab that says "Send Money". It's all really straight forward, as long as you don't over or under think it.
To find shipping weight, weigh yourself both with and without said item. The difference is the shipping weight. It's best to do this after you've packaged your item. Then go to UPS.com, USPS.com, FedEx.com, or DHL.com and use the shipping quote feature.