Often the oven will have to be removed from the housing in order to obtain the correct model and serial number information but it is also often the case that the oven has to be removed so as to effect a repair. Many people see this as a daunting task thinking that it is hard to remove the oven from it's housing but, in almost every case, it really isn't difficult at all.
Most ovens are secured into the oven housing by way of either two or four mounting screws just inside the oven door, on the lip. you can see the most common layout in diagrams 1 and 2 below.
The arrangement shown above is, by far and away, the most common method used to secure a built in oven to the housing.
To remove the oven locate the four (usually pozidrive, star or cross headed) woodscrews and simply unscrew those. These will normally be the only screw heads that you will see in the areas indicated by the diagrams above.
Once these screws are released you should be able to slide the oven out from its housing.
You can also have a problem as installers like to give us engineers a hard time and sometimes you will find that the electrical supply cable is not long enough and this can cause problems when removing the oven completely. However, if you are only looking for the model number you should be able to get that even if this is the case.
Also if you do have to remove the oven completely do be aware of any gas supply pipework, ensuring not to disturb it or you will require a CORGI plumber or appliance engineer.
You will find resecuring the oven a simple reversal of this process.