He will let you pass the barricade for 500 RU. Save your game and wait until the soldiers got rid off the stalkers and speak to the soldier towards the left of the bridge (close to the debris, not the one at the campfire!).
Once you have the silenced handgun and ~500 RU you should make your way north towards the bridge where you can see 4 or 5 army soldiers engaged with a few stalkers. At that point you should already be able to but the silenced handgun and have some spare change (ideally just over 500 RU), if not then do a side-mission for the stalker you just saved. Go back to the camp you begin the game and sell the collected guns.
Play the first mission (rescue a stalker from some raiders) and collect as many items as you can from the fallen. Hint: Easy way to get hold of a AKM-74/SU, a RGD-5 Grenade and 2 anti-radiation caps very close to the beginning of the game: Then type the following codes to unlock bonus game content. Go to your STALKER-folder in your start menu and select 'Unlock Code' (alternatively go to your installation directory and run setup-bp.exe). S.t.a.l.k.e.r.: shadow of chernobyl cheats, cheat codes & hints
