Well a model number would nice.
There are a few you know, but I will take stab at it.
The modern type you can remove the front to gain access to the heater, the latter its on the back.
The modern one you need an 8mm socket to remove three screws under plastic kick plate.
Remove two screws from door switch, place a flat blade screw driver under door seal spring ( located at bottom of door) prise off, pull off door seal and push inside drum.
Pull cabinet front from bottom towards you, there are two locating pegs at the top which locate in the timer/drawer part.
the heater is in the centre bottom of the unit and has two wires and a multiplug connected, If you remove the two wires and have a multimeter set to OHMS it should read between 20- 25 ohms, if it does the heater is fine, the multiplug is a ntc device which uses resistance to monitor temp.
You need an 10mm socket to loosen centre screw and a lot of strength to pull it out as the rubber seal as been compressed for quite a while. After removal, check you replace with same as stamped on removed heater.
To replace heater same in reverse, however place a screwdriver in door switch , set machine on rinse, let it fill up to just above heater, to check for leaks, if ok set to drain, replace font etc.
Hope this helps
If its the older type re-post it with the model number please.