Would start by checking Fuse 602

'display has a few blotches'

Your plasma display (you do have orange plasma dots, right, no aftermarket colordmd or anything?), has two connectors.

The skinny long ribbon cable. First thing I'd do is reseat the ribbon cable.

The next thing I'd do is check the voltages on the other connector.

If you are missing a voltage, it's quite common for the display driver board to have a failure in it's power supply section. This part of the board gets hot, and is medium-difficult to repair, though kits exist:

https://www.marcospecialties.com/pinball-parts/WPC-SEMIHV20516

A much easier option is just to buy a piggyback board that is easy to install and replaces the blown up power supply part of your DMD controller:

https://www.marcospecialties.com/pinball-parts/A-14039-SAT

https://www.pinballlife.com/williamsbally-dmd-high-power-replacement-board.html

Of course, re-seat the ribbon cable that goes from the CPU to the sound board to the DMD controller. This is a frequent source of problems.

The actual plasma glass display can fail, and can fail suddenly. In that case you are looking at $500 to buy plasma from Marco, or getting a LCD color replacement for the better part of $500. The good news is that the color display is awesome for your game, and worth doing.

Let us know what you find.

For grins make sure the ribbon cable is plugged in the right direction. If it is the DMD, you can get a Pin2dmd for a half the price of color dmd. Pinside member Phoerber was selling them for WCS. They look nice.

https://pinside.com/pinball/forum/topic/world-cup-soccer-94-owners-everyone-welcome/page/169#post-8003570

If indeed the high voltage section is failing as PinRetail described there are a few options, listed here from cheap to expensive:

1. Rebuilt HV section by soldering all new parts on the PCB. A kit with parts will cost you about 15 USD. However most likely your plasma screen is degassing and will draw more and more power. Therefore it might be a temp fix as it will fail again and it is only for experienced soldering champions.

2. Ready made Piggyback HV section board. About 70 USD. Same disadvantage as above: might be short lived solution.

3. Replace dmd with low voltage monochrome version. About 220 USD. Because of the low voltage you connect it to the 12v pwoer on the board and the HV section will not be used. You can remove fuses F601 and F602

4. Replace dmd with Pin2DMD. It is color and low voltage. About 220 USD

5 Replace dmd with ColorDMD. Color and low voltage. 500 USD+

When it happened to me I choose option 4: best value for money.
I am not keen on option 1 or 2. A 30 year old plasma DMD is end of life: get rid of it.

You stripped the playfield down. Is it possible that the wire cage above the VUK is off center now?

You pretty much don't EVER oil anything in a pinball. But one exception is the kickout's for the saucer. That little pivot point usually benefits from being pulled apart and a drop of oil put on it when you reassemble. (slingshots are another point where a drop of oil after being cleaned is a good idea).

Most of the reason a saucer kick out won't get good transfer of force is that it is out of alignment (odd, if you haven't taken this off the bottom of the playfield...), or the spring, on the two parts of the 'C' in this mechanism is too weak. This pretty much only happens when someone sabotages your machine. Someone has to put a weak spring here. Or the strike point of the 'C' mechanism is flattened.

If the guide plate above the saucer wasn't tightened down, that can use up some force and not allow the ball to get to the goalie also.

All of these are unusual mechanical problems. Look hard at how the mechanisms that are doing strange things are working. Make some adjustments.

Also, make sure your pinball is level, and set the playfield pitch to 6.5 degrees to 7.0 degrees (there is an app for that on your phone).

Let us know what you find.