728i - eine Gute Wahl?

Zuerst möchte ich mich für das Schreiben auf englisch entschuldigen.
Ich hoffe Sie würde lesen meine Anzeige irgendwie (Sie können auf Deutsch reagieren).
Dank im voraus.

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I would like to buy a 98' E38 728i (in France). I've seen one at a BMW Dealer with ~135.000 km.
I have a few question (those newbies always ask!!):

# Is there any known problems to check on that L6 2.8 engine?

# About servicing.
How much could I except to spend for servicing/repairing per year (at a BMW dealer)? Servicing/repairing cost me around 2300 euros in average per year with my previous car (1990' Porsche 944 turbo) and I wouldn't have to spend more than that!

# BMW Europlus Garantie
How interesting is the BMW Europlus Garantie? The 728i that I have in mind got it.

# 728i vs. 740i
Is it worth to spend more and get a 95' 740i? I guess servicing is more expensive on the 740 compare with the 728. Is that right?

# Audio System
I've already got a Navi-audio system in DIN format (Blaupunkt DX-R70 Travel Pilot). It seems that the E38'dashboard does not have DIN format space and the audio system is splitted into several pieces. Is it possible to get a kind of "adaptator" to fit a DIN format audio system?

Again sorry for writing in English. Thanks for your comprehension.
Next time I'll try a message in German.

Viel Dank,
AlyaParis