The nunchuck cable is soldered onto the nunchuck's main PCB, so you'll need a soldering iron to unsolder the old cord and also the solder on the new cord.

To prevent corrosion in the future after removing corrosion from affected Wii remotes, I would recommend using rechargeable AA batteries: so, nickel metal hydride (NIMH) instead of alkaline.

This is because there NIMH batteries will not leak when used properly under the same typical conditions that alkaline batteries do. NIMH batteries are slightly heavier compared to alkaline batteries, but I think the trade-off is worth it. I have done this battery type conversion for another item that constantly faces risks from leaking/corroding alkaline batteries: using the TI-84 Plus or TI-89 Titanium graphing calculators.

Source: this video from YouTube comparing alkaline and NIMH batteries.

You linked to 99.9% isopropyl alcohol. Alcohol shouldn't damage the hard plastic or the motherboard, as long as you don't drench the whole motherboard in alcohol.

Also, if you're talking about the small pieces that help the battery cover stay on (the 2 that are diagonally positioned from each other), then you might not have to worry if those small inserts are actually not made of foam in Wii remotes. However, in 1 Wii remote that I worked on, those pieces were made of foam. However, cleaning them should be fine as long as you don't rub away on those pieces too roughly.

There is a "slick" method to remove the combined battery terminal, which is pushing the plate through the slot, as shown in this video (timestamped):

https://youtu.be/6U0nfYUxhPE?t=175

There is also a "rough" method, as shown in this video (timestamped):

https://youtu.be/aXL-fw7B_Bg?t=43

I've used the former method, but I haven't used the latter.

I found the screw on position 3, around the CPU heatsink, to be stubborn enough that I stripped the screw with a Phillips #1 drive bit. If you find yourself in this predicament, don't worry - in my case, I discovered that using a flathead #2 drive bit helped me get out of this bad situation (for long enough to loosen and tighten this CPU heatshink screw, at least until I obtain a replacement M2x2.5 size screw).

Somehow I find the screws for the T480s bottom cover to be slightly more prone to stripping, compared to the ThinkPad T480 and X1 Carbon Gen 6. However, the #1 Phillips screws on the T480s have drives that are cut in a way that also let you use a #3 flathead.

I just checked on my model of the T480s, and I don't believe the vertical pair of screw holes on the left are actually part of the fan/heatsink assembly. I know I bought my unit used, but these screw holes also came empty. Despite having visible threading that can accept a M2x2.7 screw (I don't know if this is the actual size of the screw), only the 4 screws around the CPU are the screws physically securing the combined fan/heatsink assembly.

* The battery contacts that remain on the rear half of the plastic chassis can be pushed out, as both terminals are actually on the same metal plate. This is how you would clean, if battery corrosion got on this pair of battery contacts. See this video (timestamped, and watch for about 10 seconds) to see how to take out this metal plate. If battery corrosion isn't that bad, then maybe you can just use vinegar to clean away the corrosion, as shown in this video (timestamped).

* On the other hand, the other 2 battery contacts are both each individual metal contacts, and each is soldered onto the main PCB of the Wii remote. If you really need to replace these battery contacts, then you'll have to unsolder either one or both of these terminals, as shown in this video (starting with the device already disassembled). This site sells new battery contacts as a spare part.

I think these would include the 1 piece you need, but you would get the rest of the conductive rubber pads as well:

* ZedLabz conductive rubber pad button contacts kit for Nintendo Wii remote

* Contact kits for Nintendo Wii remotes conductive rubber pad button replacement

* ZedLabz conductive rubber pad button contacts kit for Nintendo Wii classic pro controller

The first item would probably work.

You have to unsolder the cable if you want to replace it. See this replacement cable for the Wii nunchucks, where the description says at the bottom:

Requires internal fitting and soldering to install