replace usernames with displaynames - need function location help

[create365]

Hello.

So I need to add a value to datastore, so it will be available as style variable.
I need to do the same, as the function that displays username (in post, etc), so it will be available via $postinfo, like $postinfo['myvariable'] and other places within vbulletin.

So I guess it will be a low-level function of vB and probably I have to add my own hook there as there will not be any.

I'm writing a plugin to replace shown usernames with display names set by user. Logging in, etc still with username.

Any ideas on how to achieve that?