I am just wrapping up my first WordPress plugin and the last thing I would like to do is take a piece of data that the plugin knows about (from wp_options table) and display it in either the header or footer of the site. It will simply be a small styled div with a 6 character code in it.
First of all, is this even possible? Does a plugin have the ability to modify a users theme?
If this is possible, what are some best practices and/or "gotcha's" to keep in mind when doing this? Obviously all themes are quite different so I want to approach this in the most generic and unobtrusive way possible.
If a plugin cannot do such a thing, I would have to imagine that it can write HTML somewhere when content is rendered, again what are best practices for handling this sort of thing?
This is my first stack exchange post without any code but since this is generic question and not specific to any particular method (yet) I feel that it is still appropriate.