I’ve looked at both our cars Kia and the Touareg and yes it is doable. Let’s face it fitting a caravan battery is hardly easy physically so the cars should be easier.Doesn’t look easy but it looks doable.
View: https://youtu.be/q6nQaXiZ-bo?si=0xQ6JA6u5gxIt1ue
Just had a look online and you should be able to pick up suitable batteries for £250. Try GSF car parts and enter your reg. number - I have no affiliation with them it's just that they were the cheapest when I bought my battery last month.
What doesn't make sense is that they want more to fit the auxiliary battery than the main one, is that buried in an even less accessible place?
But both cars need this doing:-
Taken from Touareg site
After replacement of a battery on the 2016 Touareg, unfortunately, it is true- The battery data of the new battery must be entered into the data bus on board diagnostic interface control module after installing a new battery.
I know first hand my local mobile chap has a lap top that talks with both cars so it is not purely the domain of a main dealer.
And I suspect the batteries all come from the same wholesaler?