Some of this has been said, but just for clarity:
when a capacitor lets go it "lets the magic smoke out" - that's electrolyte. if you have zero experience doing any soldering or electrical repair I would suggest either A) go to junkyard and get another ECU (check that it is in better shape of course) B)take it to a ma/pa electronics repair shop. They can "re-cap" it (replace capacitors) for a pretty minimal cost. If you have enough knowledge to be dangerous, then you can recap it yourself, unsolder a cap (one at a time) and replace it with the same micro-ferrad rating and either like or greater voltage rating (you can only go up in voltage - meaning they are rated to take more volts than what the circuit requires), don't go down in volts or change the uF rating. The large silver stripe is the polarity, replace them the same polarity orientation they came out. (Hint take a picture of each one before you pull it for reference in case you get screwed up, distracted, etc)...
Typically when a cap gives up it lets out a light brown powdery mess, bulges, and might even split open the top (that little X scribed in the top is a blast cap - pressure release device) being blue I would consider that to be more likely corrosion, but either way I would remove and test (which is something I would have to google up to remember how to do).
you can use rubbing alcohol (the greater the purity the better) and a Q tip to clean off electrolyte and corrosion rather than rub the board with something and risk damaging the PCB
some places to get capacitors digikey, mouser electronics, amazon, aliexpress (note about ali - some of the vendors are selling the same stuff you have already, some are really crappy low quality components, check ratings and reviews and look for sellers with real names - like 'guandong electronics corp' instead of fly by night like 'shop03586184301398')