I was in Vietnam in 1970.
Since you are an airline employee, (I assume) buy a ticket for the last leg of your flight inbound.
When you apply for your Vietnamese Visa, you will have to specify your port of entry, HCM, Da Nang or Hanoi. You have no flexibility in traveling. Turnaround time for the Visa is quick, important if you are a pilot as you will have to mail your passport to the Embassy/Consulate. You can find the forms to apply on the internet easily.
I always went without a packaged tour. Others are right, you cannot drive a car by yourself, you *may* or may not be able to rent a moped, depending on how far you want to travel. Hiring a taxi for 1 or several days is a better way to go. Me, I look for the 50 year old taxi driver missing an arm or a leg, they will really understand why you are there.
If going without a tour, you will have to spend a fair amount of time planning your itinerary. Hire a travel agent from Saigon/HCM city on the net to work out the details, it will not a be expensive. Do not use the agents that advertise in American military machines. They are good, but too expensive for what the root cost is.
If you are in the US, go to a travel agency in your Asian community for help. Again, it will not be expensive. Most large cities have a substantial Vietnames communities. Go into any Asian grocery store and ask for help to go to Vientnam. I am sure they will direct you.
I would recommend "disposable" cameras for a number of reasons I do not care to elaborate......they are cheap, and you can digitally manipulate the picture afterward......
If you are an American, get an international drivers license from the AAA for the moped. It will help, cost only about $15 bucks or so.
If you plan on taking a train from HCM get your tickets before you arrive. Especially if arriving around Tet (Lunar New Year, about February).
Talk to your doctor before you go. He can give you preventative measures against certain types of intestinal diseases. I still have some kind of mold that show up on the armpit, elbows and crotch when it is hot and humid. Crud, we called it. Doesn't hurt and now is more like an old friend.
Take some things you can trade for souvenirs with you. If you are going up into Yard country, bring some of those Exacto carving sets. Try to bring tools instead of clothes or toys.....
If you were in the infantry, do not bring old tactical maps with you. Scan them, and send them as email to yourself as a .jpg. You can print them at any internet cafe in country. Much of the country has changed dramatically, and many roads have been renamed.
Most of the Vietnamese people I met will kill you with kindness. Still, be careful. Everybody lost a relative in the war; be they Vietnamese or American.
Some heal, some never forget.