SSL certificate on Multisite

On an existing Multisite install I would like to install a SSL Certificate. I have read but just to make shure I am thinking right I have the following questions.

On this multisite I am using the domainmapping plug-in This plugin hasn’t been updated in two years so I think it’s better to install your plugin:
Will it be a problem to just uninstall the old plugin and install and configure your plugin? Or should I do this differently?

I understand for a Multisite installation with multiple domainnames on wildcard I will need an Wildcard SSL cerftificate and then https can be configured?

Thanks in advance,