Is there a plugin or quick fix without having to edit the index.php file......where I can make only a summary or exerpt of the post show on the home page rather than the entire article?
If you are using latest WP then you can use <!--more--> for each blog post so it will display only summary of your all posts at homepage. You can also use any excerpt plugin (dailyblogtips.com/homepage-excerpts-wordpress-plugin/) for that. DON.
You need to add it in each post where you want break articles for homepage. If you are not comfortable with that then better you use any excerpt plugin. DON.
The <more> function would go at the end of the text you want to show on the post. Everything above the tag will show and then a link to Read More for the whole post. Easier to just try it on a post to see what it does, its not like you can't remove it. Using the <more> function has its limitations though and I suggest trying a plugin with a little more control, for instance I like to show the latest post in full and then the excerpt of the rest, here is a plugin that can do that: http://www.dailyblogtips.com/homepage-excerpts-wordpress-plugin/
most themes use the function the_content(); do display the content.. in your theme's index.php file find this function call and replace it with the_excerpt(); i hope this works...