PHP / Oscommerce Expert - Get Website Working Again!

Hi, I have an Oscommerce v2.2-MS2 website but I can't seem to get it working properly on my new server; which for this website is set to PHP5.2. Some issues I'm having are: - In admin, I can't seem to select different menu options; it just stays on 1 spot and I can't edit any admin options. - Also, some of the admin text is not showing properly and instead is showing the variable name like "TABLE_HEADING_ACTION". - On the frontend, I can't seem to click on the product details page for the items I have loaded on my website; it just keeps showing product not found. I think this could be a URL rewrite issue. Please answer the following questions in your proposal: 1. Do you have experience working with Oscommerce? 2. Do you have experience editing "[login to view URL]" and ".htaccess" files? 3. Do you have experience with different versions of PHP? Basically, I just need to get this website loading and functioning properly again. Thank you!