This is who I would choose;

Stalker = Team Leader

Doc = Medic

HighTech = Science and communications

BlowTorch = Flamethrower (remember "The Thing" What if bullets won't hurt it? Everything hates fire!!)

RoadBlock = Minigun Marv!! Bring the Minigun!!!

Spirit = He's open minded and maybe can be empathic enough to communicate with the creature!

And depending where I'm sending them, I'd send an environmental expert (cold=Frostbite, Desert = Dusty, Swamp = Muscrat, jungle = Recondo, if not too inhospitable = Outback)

Equipment? White phosphorus Grenades, Thermite Grenades, 84mm AT-4, C-4, extra rations and comm gear. Medical supplies (for collecting specimens and treating a disease from another world).

(I've been watching "The Thing" way too much!!)