Unfortunately they removed the ability to browse uploading hosts in LW 5. They will bring it back in a later version.
Not sure about the user ID. I've been wondering the same thing. LW 4 simply used ip addresses.
LW was never designed to find it's own shared files in searches. Unless someone has already uploaded it & are online sharing the file, you will not find it.
Upload window is where you 'should' find details about uploaders, however as said above, the ability to browse them has not returned yet.
Connections window only shows ultrapeers you are connected to. 5 for pro users, 3 for basic users. If you are running in ultrapeer mode, then you will see UP's you are connected to and people who are using you as a UP to connect to the network with.