Many showrooms as well as accessory shops try to sell this to you. But if you get it done in your car, you will be having a higher chance of getting your floor corroded.
They may say that water will not enter underneath the vinyl but this is not true. Water WILL get underneath - in heavy rainy seasons, while doing pressure washes etc. Also, vinyl develop small cracks in corners and bents with time and water will enter if spilled or from shoes (in rainy season). Once water gets in, it will have a tough time getting evaporated. OE carpet (which is under the vinyl) will stay moist for longer than usual and will cause corrosion of metal sheet underneath.