I'd replace all the lines, gas and liquid, since it's not that costly. I would just hate to have a problem once I got my beer into service. As far as the tank I would take it to wherever you're going to have it filled and have them check, service, or swap it making sure the hydro date is current and that it's good to go. Hook it all up, check for leaks, and get after it. Congrats on the new homestead.