Inside the cabin, the dashboard trim cover (the "bezel") is held on with two screws at the top, going up above the gauges, and two screws at the bottom (again going up), one in the recess for the headlight switch and one in the recess for the cigar lighter. I think it's just those four, but look to see if there's one more. Once those are out, pull the bezel toward you gently but firmly. There are several push connectors on the right side, around the radio and climate controls. Pull too hard and you'll break something, but pull slowly and pry gently as needed and it'll come right off.
There's a bit of wiggling necessary to get it up around the steering column, but nothing difficult.
Once the bezel is off, you'll see the screws holding the cluster in place. Remove the screws and pull gently toward you. On the back are two connectors for electrical bundles (you'll see the locations on the other cluster you have). You squeeze the ends to release the barbs holding them in place, and just pull the connectors out of the cluster.
Not sure which speedometer you have. I think the 87 speedo has a small metal retainer that's held to the back of the cluster with one or two Phillips head screws. Remove those and the cable comes right off. If you see a white nylon "thingie" where the cable goes into the cluster, you have the 87-1/2 (newer) style. Squeeze the outer ring on the nylon retainer and the cable will pop right off.
Reverse to install the new one.
Under the hood, you need to replace the temp sensor and the oil pressure sender. Temp sender is at the back of the head, on the driver's side. It sticks up and is threaded into the top of the head. There will be a single wire coming off the top. Change this when the engine is cold, because it opens into the cooling passages, and if the system is hot and pressurized you WILL get an uncomfortable bath.
Oil pressure sender is screwed into the oil filter adapter, passenger side of the engine, just above/behind the filter. Again, one wire coming off the end of it.
