I have a small question, can you use php in the info center template? because I'd like it to check against the username to see if it's a guess and if it is then it will change its display name to Guest_"There name", but this would be a lot easier in my opinion to be done with php then it would to be done in js.

PHP cannot be used anywhere on your forum. To allow it would be a massive security risk. What you're asking doesn't seem too difficult to achieve using just the template variables with a little Javascript.