Using the wordpress plugin, how do I overide the the template files, ie EventInfo.tpl?
If you need to over ride a .tpl you can just do that by creating an extension or by using custom template folder in civicrm 

which will be more easier - also, in the time of upgrade you need to compare the file and do the changes 

More reading:
https://wiki.civicrm.org/confluence/display/CRMDOC/Customize+Built-in,+Profile,+Contribution+and+Event+Registration+Screens

https://wiki.civicrm.org/confluence/display/CRMDOC/Create+a+Module+Extension

https://wiki.civicrm.org/confluence/display/CRMDOC/Create+an+Extension

I guess this helps !!!