I'm from NH and understand the inconvenience or anxiety of inspection.
Emissions blows. If you have a car 1996 or newer (obd2), your catalytic convertor, secondary air injection system/ EGR valve, o2 sensor, and evaporative recovery system all better work flawlessly or else you will not get a sticker until whatever it is gets fixed.
If your engine light comes on for an o2 sensor and you fix it, and clear the light, all your drive cycle monitors will be reset simultaneously. These are the monitors your vehicle's computer uses to constantly make sure your car is operating within the epa's guidelines. So, once you clear the light you cannot just have your mechanic plug it in and give you a sticker. You must waste gas by driving the car for a couple days and put it through the tests so the computer can report that your car is efficient.... real nice.
From what I've heard some states like Florida don't require emissions inspection. I'm envious of those people.
Also note that none of the systems that monitor your cars emissions are actually required to make it run, they actually decrease performance! It is literally more junk that some engineers came up with that can break, cost you more money, and manufacturing this crap for every vehicle on the road most likely creates more pollution than what is actually prevented from coming out your car's exhaust pipe. THE ENTIRE THING IS A SCAM. Some "smart" people came up with this stuff...it creates jobs, revenue, and most people struggle to comply with it.
Anyway...inspection for NH includes:
Registration, plates, registration certificate and vehicle identification number.
Steering, front end and suspension.
Brakes, including parking brake.
Odometer and speedometer.
Electrical system, horn and defroster.
Lights and reflectors, including headlight aim.
Glass, glazing and mirrors.
Wipers.
Exhaust system.
On-board diagnostics system.
Body, chassis and bumper height.
Fuel system.
Tires and wheels.
I believe NH must have a very thorough inspection process due to the fact that insurance is not required. I think that's the trade off. Kinda like the no sales tax but outrageous property tax we have here
It is not easy finding a decent mechanic, who will do the required job and do it right the first time, and not gouge the prices. Ask friends and coworkers who they go to and what they've experienced. Assuming you find a decent mechanic, and if your car is in the shop frequently, build a relationship with them, make sure they remember who you are, if they have been around a while and they care they know you will remember them...and reputation is key.
Unfortunately I could come up with a list of shops not to go to, but instead I will just spread the word of a shop in Londonderry NH that my family has trusted for many years. Located on sanborn road. They are honest and don't work on everything (no tranny work, no serious engine or body repair ), but the repairs they will make are always correct the first time.
Welcome to NH and good luck.