Something Went Terrible Wrong (HELP)

I thought I knew what I was doing and was trying to upgrade things. Finally some updates from earlier in the year and then the new patches just added. Now if I go to my cart, it says Illegal Access. I can't even log in under the admin, it gives me the same messages. Please help me! I don't know what I did or how to fix it. And am going to need step by step help.

Diana

Ok, I'm trying to update with the full updated version by date. I can get into the cart again through the admin pages. But when I try and update my files in the includes/modules, it keeps telling me the file exists. It won't let me update.

Diana

Ok, I just finished updating and installing all patches. Although in the admin part is still says I need patching!?

Message: Your database appears to need patching to a higher level. See Tools->Server Information to review patch levels.

Plus if you go to shop, it is asking about the time reset. Nothing else shows up.

Diana