Hi,
1. Uh, really don't know about any good extension for site search. I am sure you can find on jed something. The best search engine for table jx would be to search all links in articles (to proccess all htmls)
2. You can do whatever you want, you have the source code and html knowledge now
\components\com_grid\layouts\GridView.php
Here you find html tags also for header. In zip you can find also css, that can be customized. Then you link css with html and get totaly new style, look and feel
Brgs!
Viljem