@marbella,
Currently no you can’t use the sortcode to insert the gallery in to the post and make the purchase there this is because of permalink, to make this posible you will have to create extra permalink for every single post on your site.
Can I ask why you want to add the galley into a post? I may be able to provide a better solution to your problem.
about the css how much do you need to change the look, if they are simple changes I can provide the styles for free, if it is something more complex please send your requirement to [email protected]