How do I save and load leaderboard stats?

Heres to save, load data.. http://wiki.roblox.com/index.php?title=DataStore

This should teach you about saving / loading data. ;D

http://wiki.roblox.com/index.php?title=API:Class/GlobalDataStore/UpdateAsync ROBLOX's example :

local DataStore = game:GetService("DataStoreService"):GetDataStore("Example")

game.Players.PlayerAdded:connect(function(player)
    local key = "user_" .. player.userId
    --we want to give 50 points to users each time they visit
    DataStore:UpdateAsync(key, function(oldValue)
        local newValue = oldValue or 0 --oldValue might be nil
        newValue = newValue + 50
        return newValue
    end)
end)

````````

local DS = game:GetService("DataStoreService"):GetDataStore("Points")

game.Player.PlayerAdded:connect(plr)
    local leaderstats = Instance.new("Model",plr)
    leaderstats.Name = "leaderstats"

    local lvl = Instance.new("IntValue", leaderstats)
    lvl.Name = "LVL"
    lvl.Value = 1

    local currency = Instance.new("IntValue", leaderstats)
    currency.Name = "Gold"
    currency.Value = 100

   while wait(5) do
    DS:SetAsync(plr.userId.."_DS", currency.Value)
  end
end)