I ahve an application that is submitting and recieving information via HTTPS. If I place wireshark on the same box and the client. Will I be able to decrypt all of the data within the communication with Wireshark? Do I need a plugin?
Wireshark will be able to decrypt the data only if the RSA key of the SSL certificate is provided to it. If the web site is not under your control, you don't have the key, therefore cannot decrypt the data.
You have other options to intercept and decrypt the traffic, though, if you can set up a transparent proxy that does man-in-the-middle attack on the encrypted traffic (and if the software in question does not verify the SSL certificate).