I do my oil changes myself. It is not hard. You could do it over at MWR's craft skills shop. You will need a oil cap tool & hex tool for the drain plug. IF you buy your oil on base make sure to get the Mobil-1 in the black label.
My two local German dealers quoted me 130 ish euros IF I bring them the oil & a tax/VAT form (19% sales tax in Germany!). I prefer to do it myself anyway. I have all my own tools so its no big deal for me. Btw.. the dealers over here charge 110 euros per hour. How much do they charge in Spain? 200 euros???
Everything you need to know is here: DIY 128i oil change.
http://www.1addicts.com/forums/showthread.php?t=301440