Used alpine air 10-11 years ago to purchase two furnaces for my home. One furnace and AC unit for a friends home . Both were delivered FEDEX two day service. We DIY installs, Both installs went perfect and are still in use today.
The AC was precharged, we did excavation etc.
Internet changed the HVAC biz.......... alot like the auto part biz where you paid full retail ( 100-150% market up ) for OEM parts because it was your only choice. Dealers are now willing to discount parts and send them great distances for 10-15% market-up.
This topic has come up a dozens times in the last few years. Some say there’s no warranty........check Alpine site. The furnaces were so inexpensive you could buy 3-5 furnaces for the price of one HVAC install. Install one and use the other two parts and still money ahead.
One HUGE caution........stay within your skill set and or have some one check your work. It’s possible to really F this up, burn the house down, CO poison yourself or other etc . Do the install and pay and permit the final checks and start up ?????
As for EPA certified.......at one time it was online open book test. That’s how I got mine 30 years ago.
The HVAC ( shop) pay for techs is the same as an auto dealer or any other service. The dealers in both cases have building, inventory, tools, equipment, training, support, service, warranty, insurance, trucks, overhead, profit etc etc. So the auto dealers tech can moon light for cheaper labor or the car owner can DIY labor their car if they both accept the risks.