Fuel gauge, oil pressure gauge, engine light

With a missing float, your fuel gauge will read "full". GM has always used a different style gauge than everyone else. As the float drops, the sending unit electrically pulls the gauge needle down. Most likely the new float got hung up on a baffle in the tank. You can verify that by unplugging the sending unit wire. The gauge should go to "full" again.

For the oil pressure problem, start by removing the sending unit to install a mechanical pressure gauge so you can see what the actual pressure is. If it really is too high, suspect blockage in the pressure relief valve in the oil pump. That commonly results in exploding the oil filter.

When the Engine Computer detects a problem, it sets a diagnostic fault code and turns the Check Engine light on to tell you. Chrysler makes reading those codes yourself real easy. It's almost as easy on your car but you have to find the diagnostic connector under the steering column. Use a paper clip or piece of wire to connect terminals "A" and "B" together. Those will be the only two terminals right next to each other in one corner of the plug. Turn on the ignition switch and watch the codes flash out with the Check Engine light. Count the flashes for the first digit, there will be a short pause, then count the flashes for the second digit. After a longer pause additional codes will flash the same way if there are any.

Nope. When it's hung up, it's stuck on something and it won't move when the fuel level changes. The float arm could be rubbing on the side of the tank or be hooked on an internal baffle. I've had wires stick out when they should have been tucked into a slot, and hold the arm from moving past a certain point, either up or down. On some designs the entire arm can be flipped over 180 degrees. That will break the connection to the movable contact. Instead of floating on the gas, the arm can get bent the wrong way as the pump is forced down into the tank. Some arms just wrap the heavy rod around the plastic float to hold it, and on those, the float could pop out from rough handling.