How I did it
When the garbage disposal (insinkerator) started leaking, thanks to this [informative video](Why Your Garbage Disposal Leaks From Bottom: Disassembly - YouTube) it looked like the leak is not worth fixing. Instead of replacing with a newer disposal, I replaced it with a regular old drain. Removing insinkerator was a simple job with this short video. Using the jam buster tool I was able to get the garbage disposal out quickly and then removed the snap ring using a screwdriver.
For the new drain, I used this Snappy Trap with dishwasher hookup and EZ lock kitchen strainer. I used plumbers putty to attach the kitchen strainer to the sink and then hooked up pieces of Snappy trap all the way to the wall drain, removing the old dirty P trap and plumbing and then hooked up the dishwasher.
To test the sink, open water, letting water go in straight as well as from the sides to test the putty. Also fill the tank a little and let all the water go in one shot, this will test for leaks under high pressure.
Mistakes Made
- Did not realize plumbers putty's purpose was to prevent water leak and thought of it as glue and did not apply evenly across the strainer first time. Watch this [video](How To Use Plumber's Putty - YouTube) to learn how to use plumbers putty
- Did not remove the excess plumbers putty from the bottom and that prevented the rubber washer from staying flat.
- By not securing the sink top while installing the drain at the bottom I moved the strainer a few times (it slides on the putty) causing leaks. To secure the top, use a needle nose plier through the cracks and hold it tight on top to prevent the strainer from moving. (Watch video)
- The EZ kitchen strainer I got at the beginning also has a paper washer which will easily tear off if water leaks and then without the paper washer you don't have enough friction over the rubber washer. The metal screwing one I got later was better, although by then I have made all the mistakes that it did not leak this time.
References
Snappy Trap manual
EZ lock strainer manual