Updated found leaderboard script to R15 and now broken, please help me understand why?

Hi, me again... every time one of you wonderful people help me I get a little bit closer to not being useless.

My next issue is with a leaderboard script I found that worked but always gave me the following output: Torso is not a valid member of Model

Here is the script (updated to replace Torso with HumanoidRootPart as per my reading on the subject of Torso not being a recognised part of the model):

function onArrival(object)
local player = game.Players:playerFromCharacter(object)
	if player ~= nil then
		local leaderstats = player.leaderstats
		local setlevel = game.Workspace:FindFirstChild(leaderstats.Stage.Value)
		print("gah")
		object.HumanoidRootPart.CFrame = object.HumanoidRootPart.CFrame + Vector3.new(0,3,0)
		wait()
		object.HumanoidRootPart.CFrame = setlevel.CFrame + Vector3.new(0,3,0)
	end
end

function setupBoard(object)
	if object.className == "Player" then
		local addls = Instance.new("IntValue")
		addls.Name = "leaderstats"
		local addstage = Instance.new("IntValue")
		addstage.Name = "Stage"
		addstage.Value = 0
		addstage.Parent = addls
		addls.Parent = object
	end
end

game.Players.PlayerAdded:Connect(setupBoard)
game.Workspace.PlayerAdded:Connect(onArrival)

However, now I get this error: Workspace.Leaderboard:9: attempt to index local 'sl' (a nil value)

If HumanoidRootPart is a valid part of my character I'm not sure why it is breaking the sl variable... any guidance would be great.

Thanks

[edit] During the course of this I found that the above code was outdated and basically broken for my needs... the following is the current working model I'm using:

local datastore = game:GetService("DataStoreService")
local ds1 = datastore:GetDataStore("GemSaveSystem")

game.Players.PlayerAdded:connect(function(plr)
 local folder = Instance.new("Folder", plr)
 folder.Name = "leaderstats"
 local stage = Instance.new("IntValue", folder)
 stage.Name = "Stage"

 stage.Value = ds1:GetAsync(plr.UserId) or 1
 ds1:SetAsync(plr.UserId, stage.Value)

 stage.Changed:connect(function()
  ds1:SetAsync(plr.UserId, stage.Value)
 end)
end)

Thanks to the guidance of Phlegethon5778, I've done my best to tidy the code up a bit and updated some of the outdated methods etc (I've edited the OP to include the new code... still won't be perfect, as stated, I'm new to this!). The leaderboard still works but now the only error I get is:

PlayerAdded is not a valid member of Workspace

from line 26... could it be firing before the Player has been added to the Workspace?