Zez

trunk/db/pre-re/skill_tree.conf

Novice: {
    skills: {
        NV_BASIC: 9
        NV_FIRSTAID: 1
        NV_TRICKDEAD: 1
        WE_BABY: 1
        WE_CALLPARENT: 1
        WE_CALLBABY: 1
        ALL_INCCARRY: 1
    }
}

Just add whatever skill you want inside.
 
For you example:

Novice: {
    skills: {
        NV_BASIC: 9
        NV_FIRSTAID: 1
        NV_TRICKDEAD: 1
        WE_BABY: 1
        WE_CALLPARENT: 1
        WE_CALLBABY: 1
        ALL_INCCARRY: 1
// CUSTOM SKILLS FROM THIEF
        TF_DOUBLE: 10
        TF_MISS: 10
        TF_STEAL: 10
        TF_HIDING: {
            MaxLevel: 10
            TF_STEAL: 5
        }
        TF_POISON: 10
        TF_DETOXIFY: {
            MaxLevel: 1
            TF_POISON: 3
        }
        TF_SPRINKLESAND: 1
        TF_BACKSLIDING: 1
        TF_PICKSTONE: 1
        TF_THROWSTONE: 1
    }
}

iirc, those are in the Clients System/towninfo.lub
 
Note: Not in the grf but in the game directory

it's entirely clientside in client\data\luafiles514\lua files\signboardlist.lub 
and thus can't be disabled server wise.
    {         "prontera", // Map         159, // x coord         192, // y coord         10, // sign height         IT_SIGNBOARD, // type         "유저인터페이스\\item\\al_warp.bmp", // ressource path         " Warper", // Text shown         "#0x00FFFFFF" // Text color     }, You can simply empty that file.

Its the enxrypted one from kro. You need to edit the one from your custom grf. It's part of the Translation files in there.