https://www.pelicanparts.com/techar...or/38-WATER-Replacing_the_Radiator_stTest.htm
This site is one I went to get the instructions on changing out the radiator on a mk4 tdi. As most have said before, the best way to do it is to remove the front grill/bumper assembly then remove until you get to the metal frame that holds the radiator, AC condenser and fan to that metal frame.
Removing rusted bolts is a tedious thing but stripping bolts or snapping heads isn't good. My advice is to add a penetrating oil to the older rusty looking bolts and leave it soaked for a few minutes before attempting to remove. If they are really rusted and stuck in, bust out a propane torch and heat the bolt while adding some more penetrating oil. Nominal force should be used for attempting removal and of course a good wack with a hammer might also be the thing that breaks the bond between the threads too.
You have likely done the repair already but I am posting some tips in case someone else comes along that needs the knowledge.
Firstly, if you happen to buy a new rad, see if whomever is selling it can sell you the little square plastic mounts for the 4 corners along with the rubber grommets because the stock ones may be damaged and they are absolutely horrific to attempt removing when you are doing all that work.
Secondly, as well as the mounts, you should get a new plastic reservoir coolant bottle. They should cost about $50 or less with the added peace of mind that you will have the repair work done right. You could go extreme as well and do hoses depending on what you are seeing too.
Pro-tip, if you have a small leak and are trying to determine if the coolant reserve tank is your faulty part, top up the system with extra water (I'm talking fill it higher than the MAX line on the reservoir tank) then jack the car up (at the front end only) and let it run until the system is hot. If your coolant is leaking from the reserve tank, that coolant will likely travel through the metal flashing and come out at the middle of the car.
I got hit with a double-whammy recently. Both the small break of the coolant at the radiator's passenger side bottom was present and very much intermittent. After replacement of the radiator, the proper system pressure revealed the coolant reserve tank had a leak along it's common fault line. Thankfully the addition of a new reserve tank is working well.
Hope this is helpful for someone else.