Unless your condensor is blocked I wouldn't reset a faulty thermostat, it's a single shot thermostat unlike the resettable next to it.
If theres no blockage you would need a heater assembly with a pair of new stats.
Can you confirm the model number. If it is IWC 71252 they have a Sole motor and when the motor brushes have worn the door locks and nowt else happens.
They are held on with a 5.5mm socket size screw. Lean the machine securely back to the wall to remove and check them.
All that muck inside is due to the stainless steel body leaking where it joins the plastic base. There is a tank repair kit with seals and bracing brackets.
Have a close look at the lower spray arm as they split on the side seam and push water out just like that.
Don't think that model number is quite right.
Confirm the area of the leak first, watch it fill. There is a large nut on the inside holding the air break, also a clip on the air break to water softener, then it lifts off to access o rings.The two black o rings are visible in your picture.
Being made by Smeg, the usual leak is the two o rings, air break to water softener, to the left and slightly above your red circle.
Watch it filling to confirm, it runs down to the area you have marked.