Just out of paranoia, if you replace the warning lamp switch w/ a sender, try to find a gauge sender w/ 2 terminals so you can keep the lamp or install a buzzer. VDO and others make them.
Ensure you check to ensure you have the proper threads for your task. Most of the older Toyotas used 1/8 British Pipe Thread (BPT) for their senders (28 threads per inch). You might have to buy a BPT-to-1/8" NPT (27 threads per inch) adapter. They're pretty easy to find online.
After the adapter I'd get a "T" or "Y" fitting like Wings&Wheels suggested to keep both the gauge and dash warning light. I have this setup on my old Dodge Daytona.