My car is close to the 3th dealer oil change. I did myself 3 in between oil change (at 6 K miles after dealer oil change). I use a top side oil extractor, that make it very easy. My cost for the oil and filter has been around $80 to $100, depending oil and filter that I use and where I get it. There are multiples choice for the LL04 oil (Mobil, Liqui Moly, Valvoline, Castrol, etc). As for the DEF, I did not have to refill it myself. You can get 2.5 gals for less than $12.
I have a NAPA near by, they carry oil (multiples choice of LL04), filter and DEF. The only item that I have to order ahead is the oil filter. It usually takes 1-2 days and it is made in Germany.