Hello and welcome

I'm so sorry to hear you lost Percy. It's always best to disinfect everything between hamsters as we never really know whether they had anything infectious or not. In addition it helps remove any scent from a previous hamster, which can upset a new hamster quite a lot.
For the lovely enclosure, you can just clean it with a spray on pet disinfectant suitable for small animals. Which country are you in? In the Uk there is Beaphar for small animals, which I use. You can also get an odourless one called Safe4 or some people use F10. If you're in the US, there will be others but I'd need to check which ones. But don't use anything like bleach or human grade disinfectants as they can leave a residue and the aroma get into the wood and plastic and off-gas.
As Socks Mum says you would need to discard all the bedding, which I think you've done already. And as she also says, any items like wood, cork or branches etc, can be baked in the oven at 100 degrees centigrade for about 30 to 40 minutes. This will disinfect them, but to be sure it removes any scent of the hamster, you could rinse them in very hot water before baking as well, so they effectively steam. Any smooth wood items you could actually carefully wash first or afterwards with dishwashing soap and water. Some things will stand that, others would get damaged. I clean plain wood platforms and shelves and other plain wood items like that and just use a sponge with a bit of water and dishwashing soap on and rinse off. This just cleans them and removes scent and gets any bits out of corners (you can use an old toothbrush for that). The baking disinfects them.
For plastic or ceramic items you can just wash them with dishwashing soap and warm water and rinse afterwards - that will remove any bacteria etc as it just gets washed off, whereas wood and cork are more porous so need baking.
It sounds like a lot but it's not so bad once you get started

Some people have put plastic and ceramic items in a dishwasher as well

I've done that before but wouldn't recommend it with anything porous like unglazed ceramic or teraccotta.
Wet tail is more commonly in younger hamsters - when they may have picked it up in a pet store and then the stress of a change of environment knocks their immune system. It is often very fast and sudden involving a lot of watery diarrhoea. It's possible Percy had that but it could have been some other illness as well. Although he was only 18 months old, that is the age hamsters are considered to be old - anything from 18 months onwards can be classed as old age and they can develop all kinds of things, whether a hidden genetic problem from birth or organ failure.
It's very sad and I think it's a great idea to get a different species. Robos are lovely.