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I pulled the one from my 88 van and i was a bosche unit very similar.
I opened it and there are 3 16V caps you can check yours, look for black vertically mounted cylindrical aluminum cans.
buy new caps, they are about 50 cents apiece or so, cheap.
don't remove the board from its case or disturb the conductive paste from the heat sink.
look for a like , looks like an arrow often sort of a broken line on the cap. note that is your negative lead, take a pic so you dont screw up orientation as polarity does matter with electrolytic caps.
clip the can about 1/8" from the board try to leave little wires poking up, the leads from within the can. you just need little stubs.
at a proper electonics bench you might use a solder sucker to extract the solder remove those leads and solder from the other side of the board but I wouldnt bother wiht that it wont be any different from an electrical perspective.
take your new caps. wrap the lead around a pin to make it like a spring 5 turns or so..
slip the "spring over the lead stub that you left that went to the cap , crimp, a dab of solder too. mae sure you tin your tip and dont hold the heat there. if the tip is dirty you will have issues load the tip with solder and wipe it off with a wet sponge and repeat till the soldering tip is clean shiny and attracts the solder not black and dirty. the soldering only takes a second, you dont have to go holding the heat on there.
Id throw caution to the wind and use lead solder and not that new crap that has no lead. you aren't doing much here..
when i did the one from my van I did slip up and clipped the corner off a transistor and I chose then to order a new ECU from Rock auto.. so I didn't test it, I decided I'd better try to replace that transistor that I damaged before trying to use it.
i think those electrolytic caps can fail due to age, the other parts there are probably pretty well ok but electrolytic caps do fail often with age.
I keep some spares, I can start my 240 with the ECU from my 740 but since the 240 has the TDC sensor and the 740 has the distributor has a different ICU, the plug is different so you can't screw that up.
there is a handy chart floating around that explains ICU and ECU part numbers and there are differences Turbos are different.
years ago I sent a car to a mechanic with a no start issue and he swapped the ECU. I blew one once by accidentally getting jumper cables swapped around. I could hear it pop when I did that.
I think they are pretty robust but I wouldn't hesitate to swap the caps again I'd just be more careful not to clip a transistor.
I replace caps in old ( hollow state) radios as a side hobby , I see lots of those fail and with newer like 70's solid state electronics its very common just to do a full swap of caps in a shotgun approach.
there is a tool you can get to check them on the board without unsoldering , Its called an ESR meter.
most of the ones I deal with are in antique radios and rated about 400 V, some are 160V.. in the ECU it will be labeled the ones in my van were 16v , this is the maximum voltage the cap is rated for. keep the capacitance in microfarads the same as it is. if the voltage rating of the replacement is higher , like double, thats ok.
You want a pencil iron , a solder station will work , a soldering "gun" usually has a big tip and you want a finer point on the iron ..
keep away from he chips and be careful of static discharge , you can work on a wood table , not metal and ground yourself so you don't build up static like you may if you pet the cat or scrub your feet in the carpet. Static discharge can kill the programming flashed on to the chips and render it dead. best to keep in is one of those static bags that they, or some other board comes in.
you can wear a grounded anti static wrist strap, or simply make one a hunk of bare wire around your wrist and ground it will do fine for that one off job.
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