Looking Seo solution for Zen cart to Magento frame work.

HI All,

I am running eCommerce website and planning to switch Zen cart frame work to Magento Frame work. My previous version working well on all search engine. so I am worry for new version sites (I keep the same domain). I want all my previous link juice to new sites. I have supple of question.
which bots, file & folders I have to blocked in Robots.txt file?.
Which process or strategy I have to follow for 301 redirections.
I have some products from third party and they dynamically calls on my site and my sites generate two types of url as www.example.com/zxy/id/product name, and www.example.com/productname/zxy/id so which one is good for seo perspective?

please give your expertise view. I dont want to hire any seo professionals.

SEO off page techniques is the best option for magento frame and zencart. http://flickspoint.com/top/top-25-ne...2015-2209.html

Gaining best quality dofollow backlinks from sites like delicious, diggo, stumbleupon and many more.

I guess the short and simpler is the URL, better it would be for SEO. If your URL has optimized keywords in it, then you might go with it. However, URL does not matter the most, it is the popularity and promotion that requires for SEO to make success.