Not too sure of the maintenance on the E55 Sir , I do know though ... it's the first super saloon I had been in ... extremely fast and I was around 13 years old at the time ... I remember the car being floored from a standstill and I was stuck to the seat .... I always wanted a E55 , however never came across anything in good condition.... I only ever sat in a stationary E60 M5 and a friend of mine had a few V10 M6s that I went in a few times ... very epic feeling everytime I went in them.a left hand suggestion. when I was looking for the E39 I saw a couple E55's solid cars and if forums and YouTube are true the maintenance is cheaper than e60 but again probably won't appreciate much. what I noted with that era of AMG is that you find more of them with documented histories compared to the BMW's of same era