Advice on modifing core javascript…

Hello,

Can someone offer me advice on what templates / core php files I should modify if I want to replace the core selects with the chose select menu? I was thinking of changing the category select from it’s current “standard select” to the optgroup chosen select found here:

https://harvesthq.github.io/chosen/#optgroup-support (First one at the top of the page)

AND…For the other select menus in premiumpress classified theme, like when you select the location for example, can use the standard chosen select so that the drop down just has the ability to search the select list and nothing more. Basically just looking to get fancy a little, not too much though.

If there is no specific guidelines I should be following, I guess I would just edit the template pages actual input code to reflect the chosen plugin, correct? Please let me know how you would do it with premiumpress classified theme.

Thank you
Brian