Adding features and modifying shader

Hi guys, I got a nice shader and I want to add more detail textures and modify the colors of them, but I don't have any idea how to achieve this, I never write a shader in my life, can you help or guide me how to do that?

The shader:

Code (CSharp):

1. Shader "Paint/Detail Material" {
2.     Properties {
3.         _Color ("Main Color", Color) = (1,1,1,1)
4.         _Detail ("Detail Texture", 2D) = "black" {} //--->One detail texture I want to have 2 or more & modify the colors of detail textures
5.         _SpecularMap("Specular Map", 2D) = "white" {}
6.         _Cube ("Cubemap", CUBE) = "" {}
7.         _BumpMap ("Bumpmap (RGB Trans)", 2D) = "bump" {}
8.         _Reflection ("Reflection", Range(0, 1)) = 0.5
9.         _SpecColor ("Specular Color", Color) = (0.5,0.5,0.5,1)
10.         _Shininess ("Shininess", Range (0.01, 1)) = 0.078125
11.         _RimPower ("Rim Power", Range(0.5,8.0)) = 3.0
12.     }
13.     SubShader {
14.         Tags { "RenderType"="Opaque" }
15.         LOD 200
16.  
17.         CGPROGRAM
18.         #pragma surface surf BlinnPhong
19.         #pragma target 3.0
20.  
21.         sampler2D _SpecularMap;
22.         samplerCUBE _Cube;
23.         half4 _Color;
24.         half4 _DecalColor;
25.         half _Reflection;
26.         half _RimPower;
27.         float _Shininess;
28.         sampler2D _BumpMap;
29.         sampler2D _Detail;
30.  
31.         struct Input {
32.             float2 uv_BumpMap;
33.             float2 uv_Detail;
34.             float3 worldRefl;
35.             float3 viewDir;
36.             float2 uv_SpecularMap;
37.             INTERNAL_DATA
38.         };
39.  
40.         void surf (Input IN, inout SurfaceOutput o) {
41.             half4 bump = tex2D(_BumpMap, IN.uv_BumpMap);
42.             half4 detail = tex2D(_Detail, IN.uv_Detail);
43.             half3 norm = UnpackNormal (bump);
44.             half4 grain = tex2D (_SpecularMap, IN.uv_SpecularMap);
45.             half4 refl = texCUBE (_Cube, WorldReflectionVector (IN, norm));
46.             half rim1 = saturate(dot(normalize(IN.viewDir), norm));
47.             half rim2 = 1 - rim1;
48.             half3 color = lerp(_Color.rgb, detail.rgb, detail.a);
49.             o.Normal = norm;
50.             o.Gloss = _SpecColor.rgb * (1 - detail.a);
51.             o.Albedo = lerp(color, color + refl.rgb * pow(rim1, _RimPower), _Reflection * (1 - detail.a / 2));
52.             o.Alpha = 1;
53.             o.Specular = (1 - grain.a * _SpecColor.a) * _Shininess * (1 - detail.a);
54.             o.Emission = refl * _Reflection * pow(rim2, _RimPower) * (1 - detail.a);
55.         }
56.         ENDCG
57.     }
58.     FallBack "Specular"
59. }
60.