Locating 500 points on the ground cheaply
Cheapest way would be to higher a contractor with machine guidance already on his excavator. Send him your coordinates in SPC, and away he goes......
A job made for machine control. But if your machine operator was set up to do that you would not be asking this question.
I've done a bit of forestry work.
For an experienced planter 500 pine bare-rooted seedlings is about a day's work, or perhaps two.
Why do you need the excavator?
What is the required accuracy? This maybe done with a consumer grade GPS if only need 30ft accuracy.
Hire a surveyor. At some point in the future, location will matter for 500 trees.
I.e. Say 200 of the seedlings die before maturity, were they all from the same vendor?
5 trees, what the heck.
500, yes, hire a professional to tie points to property line or to some reliable and established base.