Nice pick up!
I got one too. Very nice piece of equipment. Do you have the quick release valves? They come with the Deluxe version I think. Since yours came with the bio wheels I'm guessing you have them. If not, you HAVE to pick them up cuz it makes it so much easier to maintain.
As far as leaks are concerned, just be sure you have properly placed the "O" ring when putting the lid on. If you place this wrong then you may have leakage issues. Keep checking it each week to ensure all connections are still secure. Connecting the hoses required a securing band (a real pain to put on). Those bands are what keeps the hoses attached though. Not sure if you got the bands installed since you don't have a manual. That could also be a future leakage (if not complete spillage) issue.
Why aren't you using the bio wheels? I can't due to space limitations (I have a corner tank) but if I could I sure would set them up!