Do they have soundproofing service here? If so, what type of soundproofing material / brand do they use and about how much does it cost for a midsize sedan for full cabin soundproofing?

Yes they do. Call them for a quote for your vehicle and what they have in stock. They can also special order a specific product if needed.

Detailing services , full range and they do have experienced personel with 20+ years experience in disassembly of body panels, fenders snd interior upholstery , then placing it back as it came fresh from factory. I would call them about your special needs. I can tell you that they took my Land Rover Range Rover Sport 5.0L apart installed a Stealth Mode iC360 Escort Full Range Radar-Laser Refector make me invisible to any laser technology available on the planet. Wire these detectors throughout the 2.5 ton chassis without fail having a factory installed look, almost or can be completely invisable to the eyes, even installing new indicators in your speedometer housing it self . All activation stealth or in secret. Seamlessly. So to access the car panels for sound proofing is not much different than mu experience with placing balistic panels into spaces to achieve both quite ride with security of being able to survive a small arms attack. I would call and ask them to work up a quote.