After some reading online I figured that picking the tubular lock shouldn't be to difficult. Unlike a cylinder type lock all the pins are nicely accessible. One just needs a good tension wrench.
I found this link on dealextreme which offers a tool that should open the lock in seconds and enables one to make a working key afterwards. I did however pick the lock manually. The first time it took me about half an hour. I used some dentist tools that I had. The safe was empty but for a small screw. The next day I made (with some help) a nice tension wrench and I can pick that lock in 5 minutes now.
The batteries for the keypad can be access from the inside. They had leaked and it took me some time to clean up the mess. However with new batteries the unit sprang back to life. There is a small red button behind the door which enables one to set a new combination.
