you say that you require to change the thermostat I can only assume that the oven is heating but the temperature is either not getting hot enough or too hot ?
I had to buy a new element cos the old one had blown and melted but with the new element in, the oven wont turn off and everything gets burnt. It doesn’t matter what temp you put the oven on, I’ve used a thermometer probe (which goes up to 180 degrees), and it goes off the scale. The person that works in the repair shop where i bought the element said it must be the thermostat.
when your element blew, it caused a massive surge of power through the element circuit, this unfortunately weleded the thermostat switch contacts together, thats why the heat is permanently “ON”, so yes you defintely need a knew stat