VW uses that style and I have done quite a few over the years, they use this style for a reason. You need to see how much clearance there is when the speaker is mounted and the window when its down and it gets the speaker in the door panel itself.
There is a good chance it will hit the speaker in which case you have two options, either a light low clearance speaker which sounds like crap or you modify the OE speaker so you can use the outside shell which is the IMO the best way.
This is one of those times I wish I would have taken some pictures but I will do my best to describe how to do it. First of all Rivet nuts are a must, no special tools needed you only need a nut, bolt and washer if you don't want to buy a tool (the one that looks like a normal rivet gun works best for the small aluminum nuts) that are cheap on Amazon.
The first thing you need to do is cut the guts of the speaker out leaving just the outside of the shell and the cut wires going into the connector so you can solder on to them later.
Once the shell is empty bevel the top edge with a dremel and sanding drum, that is it, time to fit the speaker. Picking the correct speaker is a must, it should be round with no mounting ears so it fits into the door panel but slightly bigger than the original so the mounting bolt holes extend just outside the shell. Usually if the shell is say 6" then a 6" round speaker will fit nicely just make sure the mounting holes are outside of the plastic shell.
A 3/16 rivet nut should work fine install them in the door where the OE rivets were and get machine screws long enough to go through the speaker, down the outside of the shell and into the door. Measure the distance from the door to the underside of the speaker and get some nylon spacers from HD or a hardware store with a hole through them to take up that space, this is to prevent over tightening of the speaker.
Once its all figured out attach the wire to the new speaker using the spade connectors and make a pigtail, solder these to the correct + - wires you cut off the OE terminal on the shell so you can use the OE connector. If you cant get that just hollow the old connector out on the shell and run them through it.
This is a 20 min job per side and easy to do, sorry if I made it sound more complicated than it is.