The stand-alone mod S.T.A.L.K.E.R. Anomaly aims to be the most stable and customizable experience for fans of the S.T.A.L.K.E.R. games. It's powered by the Monolith 64-bit engine, a custom fork of the X-Ray engine.
Pay a mechanic a small fee to use their workshop. With the right toolkits and materials, you can use it to repair, craft and upgrade your stuff by yourself.