mention of tools and ability has to include some warning about how these things can work out when we buy. First the regs we see for sale are not always built for CO2 unless we really check, So if it is for some other gas we CAN remove the old pipe nipple that it comes with and screw in one with a CGA 320 type tipe. Different gases use different tips to avoid any possible mistake on which gas we are feeding. you don't want to get CO2 instead of O2 if you go to the hospital!
But that change can get into a large problem and it pretty much depends on luck how much equipment it takes to get the old one out. Having a good way to hold the reg, like a vise and then a good wrench to give enough torque to break the old one loose is critical. Not hard for some but it can be close to impossible if you are holding it on your lap, etc. Just to be aware?
And then when going back, locktight is not the right then as we are not concerned with it coming loose but using a sealer like tape or pipe dope is what we need on the threads.
Wiring the solenoid is not usually too big a deal as it is just two wires from a small charger like for phones, etc of the right voltage to match what the solenoid uses like 12 or 24 volts. Either wire to either connection is okay for this and we can often get small lugs to crimp on the wires and then slide on the lugs of the solenoid. they can be crimped with something like pliers or even mashed down to hold the wire using a hammer. Finger mashing is possible, though!
I might think more people have trouble getting the old parts off than getting the new on.
The decisions are actually the harder part.