Repurposing a garage can be a good idea, but it will need a LOT of work to become a kitchen. That's why they are usually recreated into bedrooms or family rooms. You're going to have to jackhammer a large trench in the lab and connect to the home's main drain. You will also have to vent through your roof with a separate stack or tie into your home's main vent stack depending on your location. And that's just for the plumbing. There's also electrical, gas piping, and the HVAC to contend with. Maybe look at your existing kitchen again to see if it can't be more easily expanded rather than being moved entirely.

Thank you for the fast response.

Fortunately, this garage has been previously remodeled (used to be a photo studio), so the HVAC is already there. Electrical is no problem, as the panel is in the room. Venting also shouldn't be a problem, as there is a stack on the other side of the wall.

One plumber recommended putting in a grey water pump (like saniflo). We don't use the garbage disposal (bad experience), so it would be straight water.

We've also got the water supply in the same room as well.