never effect or help any template your site optimization.

It can affect if we use more graphics than text.

Changing the design might be a good thing for SEO and also a bad thing. Depending on what do you change and how. I had sites which went up in search engines by a couple of pages after I changed the design. I guess the old one was not that good and the new one was much better but it easily go the other way.

It totally depends on the actual rules of google,,,,

There is no connection between the template and seo. So you can change it knowing you will have the same seo on the site.

Yes, I think its little bit effect ranking of your site but it will be recover soon.

I Never tried to change website design but in coming few months may be my company change the website design. After that may be some effect took place as changing the website design is little bit risking. I hope nothing goes wrong as we are not changing contents or any thing else...

Well it depends on changes it could effect or it could not be I have my own site experience I change a bit of design and my site drop on PR2 from PR3 but after next crawl its gain PR back so some time search engine like changes you do and some time its not.