The patch I did on the old pump didn't help. The crack propagated and leaked elsewhere. The risk of the tank breaking apart while driving and blowing up into flames, was too great for me. So the car was grounded for a week over Chinese New Year while waiting for the new fuel pump assembly to arrive in the mail.
Fuel tank with old seal. Yes, that is a tank full of Shell RON95 flammable fuel. Don't even think of smoking while doing this. Oh, and don't try taking a close up photo of it with the flash on, as that will definitely make a nice loud BOOM! just like in the movies.
The new seal fits tightly and is difficult to apply as it tends to snap off the edges. The black colour makes it difficult to see, especially when the fuel pump assembly is fitted onto it.
A tripod holds the fuel pump assembly in place and stops the new seal from coming off, while the locking ring is being screwed on tight. Unfortunately, over-tightening the new ring caused it to break into two. So I had to reuse the old ring, making sure it was not screwed too tight.
After all was installed, I pressed the accelerator all the way down and turned on the ignition, without starting the engine. Kept it pressed for a few seconds to let the fuel pump pressurise the fuel line; I could hear the fuel pump whirring at the back. Released the accelerator and started. Voila! Everything works! No more leaks and no more stench of leaking fuel.
Image from hooman.org showing the tool for opening the locking ring. I didn't have this tool, so I used a hammer instead.