There was more angst in thinking about the work than in actually doing it.
Here's the procedure and pictures: How to replace a 540 radiator
I actually did this twice. The first replacement radiator I put in was defective. Looks like it was damaged in shipping. If you do this a couple times you can get quite good at it!
Although my car is an automatic, there were no connections to the transmission to worry about. Maybe that is also the case on 94 540i's.
This diagram may be helpful: Radiator Parts Diagram
Since I had to be up under the car anyway, I took the time to flush the cooling system. This is a little more involved; you need to drain coolant from the block, too. There are drain plugs on either side of the block.