No, you cannot use any lubes in that diff. It has screws holding the cover on, but there is no seal. So as stated before, you only want to use grease in it because anything liquid will leak out.
Most, if not all marine grease is not safe for plastic. You need SYNTHETIC grease.
And no, don't...
I am sure some of the other Traxxas shocks would fit it, but I don't know which ones. Do you have calipers handy? You can measure between the mounting holes with the shock extended and compressed and get the two measurements and do some looking around for shocks with those measurements.
Yeah, that's recommended.
@STONER RC can give you some pointers on brightening up that white plastic. He did a restoration on a vintage kit with white plastic that looked like new when he was done.
The one in the center where the outputs go is a bushing, not a bearing. Yeah, replace that for sure. Fast Eddy Bearings might sell a complete set for your car. There is also a seller on ebay by the name of "Winter Evening" that sells good bearing kits. You can message him and he will put custom...
Whatever grease you use, make sure it is synthetic and not petroleum based. Petroleum based will melt the plastic. I use Mibile 1 synthetic grease anywhere it may come in contact with plastic.
Mobil 102481 1 Synthetic Grease https://a.co/d/jkq3voL
Ok. It gets a little scary here. You have to gently pry the ears (arrows in pic) apart on the driveshaft on the side by transmission to remove that ball shaped swivel to be able to access the screw. The plastic being as old as it is may make it brittle.
Dude. That thing is a museum piece. I would shelf that one and buy a new Rustler to play with if it were me. Did you get a body with it? If so, how is it?
If it were me, I would keep it as original as possible. I wouldn't change the wheels unless you absolutely had to. There will likely be tires that will fit it. Sometimes you can find some vintage Duratrax tires on ebay that will be close to the stock style. I would definitely put the same tires...
Do you have calipers? Remove your tires and measure your wheel to see what size tires it uses. The car being that old (1989), it will likely use a 1.9" tire, or possibly even something not a standard size.
You'll be very lucky if you find parts for that because that is a rarety right there. I would go on ebay and search for that RC. After you do, save the search and set a notification so you will be notified anytime anybody lists a part for it, or a complete RC.
Another tip - if you see anybody...