Can network administrator sniff and decode SSL traffic to get sensitive information like Gmail password, Skype password, Windows email account, or Remote Desktop .... ?
Whether or not a VPN tunnel is used, network administrators cannot inspect SSL traffic unless they either have access to the server's private key or use SSL deep inspection.
SSL deep inspection replaces the server certificate and requires an alternative CA root certificate to be installed on all clients. You can easily detect this by inspecting the certificate chain. SSL deep inspection uses Man-in-the-Middle decryption and reencryption, and should be well documented and policed inside the company.