Should you wish to change it early, every 6 months or 7,500 km (whichever you reach first) will be sufficient. No need to change it every 5,000 km.
Otherwise, oil change intervals are normally every 12 months or 15k.
Definitely DIY if possible.
Regarding warranty, as long you use genuine parts and any VW approved 502.00 oil (minimum) or 504.00 oil (preferred), you should be fine.
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