Currently I only know how to get both X and Y's Scale and Offset positions
guiObject.Position = UDim2.new(0, 0, 0, 0)
How am I able to just change the Position Scale value of X or of Y? (1st and 3rd of the 0's)
You can reference the scale to keep their values.
guiObject.Position = UDim2.new(0.5,guiObject.Position.X.Offset,guiObject.Position.Y.Scale,guiObject.Position.Y.Offset)
This will only change the X scale.