Installing Upgrades and Other Plug-ins

Hello to all.

I just joined hardly few minutes back and I'm loving it!

Anyways, to begin with, please excuse my understanding level as I'm a total beginner at WPMU.

1) There are SEO Enhancing plug-ins which I need to install in /wp-content/mu-plugins/ directory. So I have uploaded the plug-ins directly in .zip file as it is when I downloaded from the site. Now what do I have to do? Leave it? Cause I don't see any change in the Admin page.

2) I have unzipped the Upgrades plug-in and uploaded different files to different directories as instructed in the text file. But when I visit 'Plug-ins' page in my Admin page, I don't see anything new. Can you please explain it easily?

3) I see the following message in many plug-ins. "If the auto-install does not add the db table(s) for you then run the sql code in "sql.txt" on your wpmu db" What does this mean?

Thanks a lot for your help!