OsCommerce is a great bit of software and would certainly make creating an online store much easier. For anyone who doesn't know OsCommerce is an open source PHP e-commerce solution and can be downloaded for free at click here
To answer your question you do not need to implement SSL as all payments will be done through PayPal and they use their own secure servers. This makes things a lot easier for you as you can just put the site on a normal http server.
Make sure you secure your admin area and make the config files read only.
Good sites you might want to look at:
OsCommerce Knowledge base - click here
OsCommerce Forums - click here
OsCommerce Documentation - click here
Hope this is of some use