For your image issue, it is one of the more common questions on this forum.
http://forum.x-cart.com/search.php?searchid=1179246
As for the "There are no available products under this category" issue, that is most likely in the language section of your admin - not a file directly. To get to it, Admin > languages > select english > search for the phrase you want > edit it how you see fit.
As for the phone number issue, Admin > general settings > company options > edit the info as you see fit.
Good luck and do not forget to search the forum. There are tons of helpful posts out there.