Forced excerpt and custom sort for MarketPress listings?

I am in the process of building a site with similar features to that of eBay and Etsy which will allow users to create their own store and sell products to their heart’s delight.

1) The use of a [more…] tag for displaying excerpt descriptions not only does not appear to work, but is inconvenient. Is there a way to force the sidebar widget to display only a certain number of characters without having to hard code a ‘char_limit’ restriction? We would rather that user need only enter the desired description and let the website do the work of appropriately abbreviating and displaying it.

2) We would also like to allow vendors to advertise their products which would essentially bring them to towards the top of the pile. Is there a convenient method to give precedence to advertised products in the display list?

3) Finally, the wp-admin page is too “techy” for our purposes so we will be creating a set of custom product creation and store management pages. I apologize for not digging very deeply into the plugin yet, but a lot is on my plate. Does this plugin allow for easy hooks and adaptation for this purpose?