Welcome to the board Brendon! The Vietnam series was produced between 1995 and 2000. The sets included: The Air Cav (First Cavalry, based on the movie Apocolypse Now), The Patrol (a grouping of grunts from the Big Red One), A Huey Helicoptor in either 1st Cav or U.S.M.C. markings, or a medivac version (recently discovered), an M113 Armored Personnel Carrier (either wood and metal or resin and metal) in either US Army or USMC markings, two different sets of Marines, a set of Vietnamese villagers (a mama san & papa san selling fish and fruits on platters, along with a boy playing a flute on the back of a half submerged water buffalo), and a set of Viet Cong. There was also a resin and metal "Duster" antiaircraft tank (very limited production).
I recently discovered that two other Vietnam Era choppers were produced, a Bell Jetranger Kiowa, and a Hughs Keuse.
Andy also produced two dioramas for Vietnam: a special order Firebase (made in either six small parts or two large parts) and a Tet Offensive Street Scene with a Temple Compound being shot up and a Street of burning town houses in the background (only 4 made).
As far as values, the figure sets seem to go for around $200-$300, the Huey recently sold for more than $900 on ebay. The M113 APC hasn't changed hands on ebay, but wood vehicles of the same vintage have gone for $1500 to $2000. The Duster is extremely rare (Andy thinks about 5 were made) so if one were for sale, I would expect it would crack $1000. The Dioramas ran around $500-$750 retail, so if one became available I would expect it to fetch over $1000.
No Vietnam sets are in current production. Andy keeps saying he would like to produce updated versions with todays level of sculpting and painting, but hasn't got around to it. If you want to see all of the Vietnam sets, including all versions of the vehicles, on a firebase diorama, check Bill Sager's website, which has some photos of mine. I also have a portion of one of the four Tet Offensive Street Scene Dioramas, but I have displayed as part of a WWII Dutch Village (probably Eindoven) Market Garden Diorama. In the Photos, the temple, a wall section, and piece of the courtyard form the far right of the diorama (where the Tiger Tank sits).
I hope this answers your questions.