1) Get the OGSE 0.6.9.2 R2 installer here: Deathdoor.ru or in the downloads section.
2) Get argus_tex_pack_1.0.7z from Playground.ru (optional)
3) Get the creatures pack (0.51 + 0.6) from Playground.ru (optional)
4) Get the db unpacker in the downloads section.
5) Get English configurator here: Deathdoor.ru or in the downloads section.
6) Get the alpha version (user-made) of translation here: Deathdoor.ru (it relied heavily on Google translator that's why many quests and dialogs may be very confusing) or in the downloads section.
1) Run the OGSE installer. Configure it with the argus pack and the creatures pack (optional). It will install three db files and configurator.exe file into your stalker directory. Plus it will create a gamedata folder in the Stalker directory.
2) Rename the Stalker/gamedata folder to Stalker/gamedata_temp - we will use it later
3) Create a new Stalker/gamedata directory
4) Using the unpacker unpack gamedata.dbe into the Stalker/gamedata directory
5) Using the unpacker unpack gamedata.dbf into the Stalker/gamedata directory
6) Using the unpacker unpack gamedata.dbg into the Stalker/gamedata directory
7) Move everything from the gamedata_temp (created in step 2) to the gamedata folder, replacing files as necessary
8) Extract the textures directory from argus_tex_pack_1.0.7z to the gamedata directory. WARNING: don't replace the textures.ltx file (optional)
9) Extract the textures directory from creatures_0.51.7z and creatures_0.6.7z to the gamedata directory. WARNING: don't replace the textures.ltx file (optional)
10) Modify the gamedata/config/localization.ltx: replace "rus" with "eng"
11) Copy your gamedata/config/text/rus directory to gamedata/config/text/eng
12) Install the translation
12) Replace configurator.exe with English version
12) Run configurator.exe from the main stalker directory, choose your settings then save it using the button Apply. Afterwards you can either use the configurator to start your game, or simply use your old shortcut.
Note: The game will be much more stable if you start it from the configuration utility with "no prefetching" option ON.
P.S.: of course you can delete gamedata.dbe, gamedata.dbf and gamedata.dbg files after you finished all the steps above, they are not necessary any more.