OSCommerce & ZenCart Issues & Addons needed done.

I WILL MAKE MILESTONE FOR $100.00 --- do not post more or you wont be considered. NEED BOTH DONE IN 72 HOURS. I have two projects in one I need worked on a.s.a.p OSCOMMERCE: 1. Fix checkout issue. Errors out at the last page. Could be authorize issue but we need to verify this issue; fix solution. Customers pay then see error page, they than reorder and keeps billing them. This is costly to the owner of the website and this needs to be addressed and fixed. 2. Shipping & Handling plugin. Shipping is different depending on country and weight of product -- we'd want to get a nice plugin installed; we'll buy one of needed but need you to fix this. ZENCART: 1. Add image gallery plugin. Style to look like website. (I believe their are open source modules for this) 2. 1 line of text added on shipping page. 3. Add banner to each page in php code. (be 1 banner that should show on all product pages) Need this done A.S.A.P! Thank you!!!