Crawl Errors in webmaster.google.com

Tried to search for the answer, but will Google penalize you for crawling errors.

I have 622 pages not found on my WP blog. I am assuming Google does not like this. How do "bulk" fix this without deleting each page manually???

So all I need to do is make some changes in the htaccess file? I've never done anything with the htaccess file. Can you let me know what I need to put into that file? In return send me some (or all, I dont care) of your rss feeds and I will submit them to 155 RSS places.

I've installed this plugin, but have no idea how to make it work. Is it automatic?