[Vwdiesel] 190 Benz questions

[Scott Kair]

    Today I was offered a 1987 Mercedes 190D with a stock 2.5L td engine.
The owner is ready to get rid of it due to some problems.  It started
alright for me, but I didn't drive it, and only gave it a superficial look.
    Owner described engine issue as alternator related- the battery (of
unknown age) goes dead and periodically won't start unless jumped.  Also
runs rough- it vibrates to the point of shaking- and lacks power.  There
also appears to be a fuel weep/seep/ leak in the vicinity of the pump.  The
plastic fuel filter appeared to be black inside, and owner didn't know how
old that or the main filter are.
    Climate control is screwed up, which is a given.  There was some
superficial rust on the left front fender, and very noticeable rust spots on
the left rocker panels.  Muffler is new, as in a month or so old, but the
engine was fairly loud.
    The charging issue, if that's what it is, is a concern, as the
alternator is buried.  (Serpentine belt is about 5 years old.)
    I suspect that new fuel filters and a couple of cans of Diesel Purge
might fix the rough running/ lack of power issues.
    The purchase price is very right, but not if I have to dump several
times that into it.  A quick search on ebay for Mercedes Diesel revealed
that some parts used on the 300 series 2.5's will not fit this one- I'm not
sure of the chassis designation.
    The transmission is a 4spd. auto, btw.
    Any advice or suggestions?
    TIA,
    Scott Kair