I havent updated this since the big change in this plugin. Is their a recommended way to convert old config with all my items and shops?

Uhh... just gonna half to make the jump buddie into 1.8

Wayyyy too much changed/added you could just disable both of your old config/plugin by renaming them with a - at the ends of the file names so like GUIShop.cs- and GUIShop.json- then just upload the new plugin so it doesn't mess with your old stuff in case you want to go back. 

Merged post

If you have a 1.7 config I can update it to 1.8 for you though

Yeah the new version doesn't suit my needs as well, I went back to the old version, will patch whatever breaks in the future myself.