From memory (I am at work at the mo), the Lima 92 is one of those irritating locos where the body is easy to attach to the chassis but a right s*d to remove. Before removing any Lima body from it's chassis, make a mental note of which way round the body sits in relation to the motor bogie as some bodies will not fit the other way around.
The bodies of many Lima locos are simply attached to the chassis by several locating lugs on both sides of the loco - I am thinking Class 37 here where the lugs are clearly visible under the driver's cab doors. (some classes - e.g. 20 & 47 require removal of the buffers before the body can be removed)
But the 92 is a more complicated beast. There will be several (at least two) lugs blind on the inside of the body along each side to attach it to the chassis. You will need to ease the sides of the body away from the chassis to allow the lugs to be freed from their locating holes - use a thin blade or even strong fingernails to do this. So that the lugs do not immediately relocate back into their holes, place pieces of plastic sheet between the body & chassis - pieces of redundant credit cards are ideal for this. That's the easy bit!
There will be two further, much chunkier, locating lugs one attached to the chassis at each end of the loco. In order to deal with these, pick up the loco by the body with your pieces of plastic wedged along the sides in one hand and then with the other hand, take hold of the chassis towards the centre (not the bogies) and pull the chassis sharply downwards away from the body. The chassis should flex and come away from the body. The worst that can happen is that the end glazing will fall out. This can easily be replaced and the worst thing that you will have to do is to use a small spot of glue to fix the glazing back into place.
Once you have separated the body from the chassis you will see two large lugs that are part of the chassis moulding which have caused you all this grief. Take a sharp knife and cut them off back to the chassis level. This will make body removal much easier in the future. On no account should you attempt to ease the body away from the chassis by putting plastic, blades etc between the two at the ends of the loco - there is a 99.9% chance that you will damage the body.
Once you have made your inspection and effected any repairs, simply place the body back on the chassis and the side lugs will keep it firmly fixed to the chassis.
These instructions also apply to the Lima 59, 60, 66 and 73 amongst other classes.
