As long as %postname% is included, most search engines will scan the page. The title is important for SE optimization. The default install does not include %postname%. You need to change the permalink option as you describe.
If the .htaccess permissions are set so that WordPress can read and write the file (WordPress suggests 666) then WordPress will update .htaccess, if you do the following:
1) In the Control Panel, go to Options > Permalinks.
2) Click the Update Permalink Structure button to freshly generate new rewrite rules for your permalinks.
For more information (i.e., if you need to change .htaccess manually for some reason), and for a complete discussion, go to Using Permalinks. If you want to know how to code rewrite rules in .htaccess, go to URL Rewriting.