[LetsOWN[PL]]

No problem.

First:

pawn Код:

if(sscanf(params,"d",text))
{
    SendClientMessage(playerid,COLOR,"Error msg.");
    return 1;
}

I really think, that while you are using if(sscanf(..)) condition, you've to make action below it, to be sure, that it WILL work.
Instead of "Error msg." you can write either "Learn to use command, foul" or "Error. Try again. USAGE: /skin [0-5]
Why 0-5? Look at the switch function.

Oh, forget about command header (damn).
Instead

pawn Код:

command(skin, playerid, params[])

give

pawn Код:

command:skin(playerid, params[])

if command(skin, playerid, params[]) works for you, don't edit it.

Second modification: I do not see sense, of using "if(Player[playerid][Group] == 4" in each 'case' in 'switch' function, if 'switch' function will only continue, if this condition is done

pawn Код:

if(Player[playerid][Group] == 4)
    {
        switch(text)
...