[member]

Your on the right tracks, only a few minor problems
You need to tell the timer which arguments to pass as accoridng to the wiki. We can see that you will need "playerid" handy to execute the Test function correctly., otherwise pawn wouldn't know what "playerid" is since "Test" is a custom function

Also the format should be "d" since playerid is an integer and not a string

Here's what it should look like:

pawn Code:

SetTimerEx("Test", 5000, false, "d", playerid);

forward Test(playerid);

public Test(playerid)
{
    GivePlayerMoney(playerid, 1000);
    DisablePlayerCheckpoint(playerid);
    SendClientMessage(playerid,0x48FF48FF,"Congratulations, You have won $1000");
}

The timer will execute after 5 seconds.

Good Luck.