#1 no smoking
#2 do circle check and determine whether the tank must be changed
#3 If so, drive the truck to a well ventialted area
#4 Neutralize the truck, neutral, parking brake and forktips flush
#5 Put on safety gear and shut off on/off valve
#6 rev the engine til it dies
#7 restart engine to ensure fuel line is purged
#8 Shut off engine
#9 remove the cylinder
#10 Store cylinder according to local fire codes
#11 Check new cylinder for date/damage
#12 Install cylinder with safety relief valve at 12 o'clock
#13 reconnect couplings
#14 Open on/off valve 1/4 turn, then all the way, check for leaks
#15 If all fine, lock her down

Hope this answers your question.