If he senses that his ruse is working, Vash whispers over to Thar while he orders a drink and drink his mutagen. If I知 not back in a few, come lend me a hand. He then winks to Thar with a smile. He値l take the drink in his off-hand. Once upstairs he値l enter the room, keeping his back to the door. So, over 1000 you say, how much so? As soon as he痴 within striking distance he値l eject his spring loaded dagger and drive it deep into the mans leg, followed by a 5foot step back and draw his elven blade.
If he suspects that the man is on to him, He値l skip the drink order, and instead instruct Thar to follow him up. Once upstairs (out of sight from downstairs bar patrons), he値l draw his sword and move to strike immediately.
SpoilerRolls
Checking to see if the man seemed sincerely agreeable, or if something sinister is up on his side.
Sense Motive: (1d20+5)[10]
DC20 for a hunch
Attack: (1d20+8)[23] attacking Flat-Footed AC, otherwise it's the sword at +9 (so just +1 more)
Dagger: (1d4+6)[8]
Sneak Damage: (2d6)[9]
Sword Damage: (1d10+10)[16] (6str+3str+1enh)
So no clue on the hunch, and in either case, likely a hit for 16 or 17 dmg.