I had mine replaced a few years ago by a family friend...my only concern is that since this involved piping up the gas line hopefully everything was done properly...it's been a few years now and knock on woods but so far so good..
oh and I thought he bent something and that is why my water pressure suck...but turns out, I think it was a city related issue...once they fixed my outside sewage system and started metering my water usage, my water pressure is fine now... I guess all that gunk or junk probably clog up something out on the pipes coming into my property and so after they dug up something and replaced it, it's normal now.
if ever you doubt your skills... leave it to the pros... in most homes there should be a water pressure valve in which you can control the water pressure that comes into your house... my research led me to not exceed 80 psi... 60 to 80 psi is the range... dealing with gas should never be taken lightly too... know what you're doing or else ka'boom... lol!
i do things myself because many of the time i doubt the skills of others unless i have absolutely no clue what i'm doing... for instance over the summer... i had my breaker box replaced because 1: i dare not deal with electric of that magnitude and 2: the skill required to do it exceeded what i knew or could learn... so i ended up paying this older electrician 3k, who did a phenomenal, to switch out my breaker box and to pigtail all of my aluminum wires inside my house into copper so that my house doesn't go up in flames, which aluminum wires are known to do... lol!