MKIV 2002 GTI - Pioneer MVH-P8200 Install Advice

[Jonno_WA]

After some lengthy trouble attempting to source an online calculator and trying to find the original dealer I gave up on the Eurovox OEM head unit after a flat battery.

I ordered this Pioneer MVH-P8200

The Metra 40-EU55 Antenna adapter, and I am sourcing this Aerpro Pioneer to ISO Harness 12 PIN from a local Repco for $15

Am I missing anything essential to make this a smooth transition? And, if I was to replace the stock 6-1/2" speakers in the front - which speakers are at the right price point?

[Jonno_WA]

Just incase anyone google searches this - the Metra 40-EU55 doesnt fit the VW connector.

I'm now struggling to find the wire that leads to the parking brake switch - can anyone point this out to me (I can't find the info)!