If you get rid of bin tycoon do you lose your items in your plaza

No, you still keep all of your items although you can't use them. This is because if you become a bin tycoon again you can gain your items back. Even if you're not a tycoon, you can sell the unwanted items at gongs pipenest.
Just to let you know, if you dont like the credit card pin system you can buy gift cards for just 3.95p per month for tycoon, then you know everything is safe and you WONT loose money!!!!!!!