I assume this is twin as in one on each side in parallel with the engine, not two in series - Right?
$5k better be drop the car off without turbos and drive it away a few weeks later with turbos, tuned, ready to go.
It will be hard on the transmission - plan for a new one in the near future along with lots of rear tires (or really skinny rear tires to make the transmission live a bit longer
).
Depending on your mechanic's skills and attention to detail, this might be a great thing or a dumpster fire of problems.
Do you have anymore details about the kit or what you want out of the car performance wise?