Leaking a bit of oil, like a dirty residue formed into rings by the O ring that indicates travel used is no problem. But you say the shock "has died already". Apart from the oily residue does it work fine? Yes? No problem then.
If you used the phrase "my shock has died" to the dealer, no wonder he wants to see the shock. I had this on my very first full suss (Fox F&R). I was really worried about it. The dealer told me that it will soon stop. I responded with "it will when all the oil runs out!" But it did stop and the shock continued to be fine for the next three years until I sold the bike. After each service the oily residue restarted for a week or so, then stopped. I've had a similar "problem" with Rockshox shocks too.
Look at it this way, it is an indicator that the shock actually has oil in it!