I haven't been on in a while and apparently shops have had an "update".. Everything is gone though. I had 2 shops and a gallery, where are they and where are all the items I had inside? How do I access the till to collect my SP?

most of your questions should be answered in this guide :)

the shops were moved over to a new system, your old items are safe and can be found in the commerce tab up top under your shops, with a ! sign next to them.

Not seeing a "commerce tab" anywhere, nor the pages in that link, but I managed to find the link to my shop and transfer the items. (I have the top bar CSS'd over to the left side) I can see it on my pet's page.

The commerce tab is a part of the top bar, so it's likely your customcss affects that