Their diagnosis makes sense to me, but I've seen better prices for similar services.
How many miles on your vehicle?
Since it seems like this car is not driven daily, is consider the option of shipping the cluster to them. I usually eschew haphazardly throwing LEDs at everything as they can be too harsh; but since this is a specialist shop, they might/should be able to find LEDs with suitable output so that they both look good and are functional.
Removing the instrument cluster is not very difficult.
Alternatively, you could spend a little money + some time to do as shown in that video. Yes, the Q45 setup is very similar to the i35.
I bought a used cluster from eBay. Upon receiving the used part, I disassembled both gauge clusters and switched the bulb over.
*As much as it's not a common issue with Q45s, fluorescent tubes have a finite lifespan so I'd preferrably go for newer/lower mileage parts.