Yes, you can use a wildcard SSL cert, but you will have to apply it for all proxies or make one proxy with a number of aliases (in proxy manage->settings->servers (like entering *.alertlogic.com in the alias list to match a *.alertlogic.com wildcard certificate).

Updating SSL certificates can be done in several ways. The best approach is to have the CA generate a PEM certificate (it will do that when you select Apache as the destination server).

When updating certificates, simply copy and paste the content (including ---BEGIN CERTIFICATE--- and ---END CERTIFICATE--- lines) of your renewed certificate into the correct Public key field for the Web Security Manager proxy in question. Do the same for the private key (which you should have when you generated a CSR file). Copy and paste that?? in the Private key field and press save. Make sure to type in the pass phrase in the Passphrase field if your private key is encrypted.

Web Security Manager will then replace the copy of your Public and Private key with the new copies.