How does Whatsapp store the chats and contacts of any given user, and are they recovered if one installs Whatsapp on a different phone?
Your data is stored on the device and encrypted using either an encryption key that is also in the device or a key generated based on your account. The best advice is to do as whatsapp suggests and before you uninstall anything, you make from the Windows phone a copy/back-up on your cloud (google-account). It is under options/back up. Then (re)install whatsapp on the Android and import the data from the cloud. Confirm the number and done!

Or you can try exporting a database on an SD and then try to import that on the Android, but that is definitely not suggested. It seems to never work. There are some discussions here on the matter.