Woocommerce is by far the best.

You may have some design issues with the shop page if your theme is not integrated already with woocommerce.

The issues you will get is that the layout of the shop and cart pages will not fall properly and you will need to make some changes to you php which you could hire a professional to do for a few bucks

Your other option ( if your theme does not integrate properly ) is to switch to a theme that is woocommerce integrated.

How will you know if your theme is woocommerce ready?
1 - Check your themes sales page to see if it mentions it's woocommerce integrated
2 - Install woocommerce and check the pages. If all is good then great

What if it's not?
1 - I use geeks per hour. You can use their $5 for 5 hours service and that will do it and that is so cheap otherwise your looking at about $50 - $100
2 - It's so easy to switch themes. Just find a suitably one already integrated

If you need any more help just let us know

The link for woocommerce has been posted below, just install it and see

Hi - if it helps add to the comments already made - I have two WooCommerce webshops setup and running on WA websites - and have no issues with them.

All the best, Mark

Hi
You can download the woocommerce plugin here:
http://wordpress.org/plugins/woocommerce/
If you need some further help, don't hesitate and contact me.
Have a nice day.

Webshop as in storefront? There are very few things you cannot do here that you can do elsewhere.