It seems that people approach grilling steak one of two ways: either in a casual manner or paying perhaps too much attention. Some will heat the grill with abandon, throw the steaks on, flip once, then pull them off, and serve; others will fret and worry, cutting into the meat every two seconds wringing their hands over whether the meat is done or not. Both techniques do have some merits but a method somewhere in the middle is ideal.
Re-assemble all the parts you removed, taking care to fix the burner tubes back in place in proper position with the cotter pins or screws. Rub cast-iron grill grates with a light coating of vegetable oil. Finally, re-connect your propane tank and fire up the grill; let it heat for at least 15 minutes, then turn it off again. This will help burn off any residues from cleaning, season cast-iron grill grates, and serve as a check that you re-assembled everything properly.
Check the fuel lines for invisible openings. Create a mixture of soap and water. Make sure you stir the mixture around so it gets really sudsy. Then, use a paintbrush to brush the soapy mixture onto the fuel lines. Turn on the gas, and brush some more soapy water onto the gas lines. If any bubbles form on the gas lines, that indicates a gas leak. Immediately replace any fuel lines that exhibit signs of a gas leak.