I need straight, realistic advice.  The 2.6 engine in my 1993 190E
Sportline is shot--at least two bearings burned.

I'm going to keep the car--even at 110,000 miles, it's near perfect in
every other respect, and there's nothing else I like as much.  Also, it
has a new auto transmission with less than 20,000 miles on it.

There are four options for replacing the engine:

1. Let the dealer do it with a new long block from Metric Motors--4
year, 50,000 mile warranty.  Cost--at least $8,000.00.  (Dealer will do
a short block, but says the cost will most likely be about the same, and
 only 1 year warranty.)

2. Buy the long block and do it myself.  Long block, with shipping,
about $5200.00.  Plus whatever other parts I need--engine mounts,
gaskets, etc.  4 year, 50,000 mile warranty on long block.

3. Buy a short block and do it myself.  Assuming head is OK, about
$3100.00 plus other parts and machine work on head, etc. (Warranty on
short block is 1 year, unlimited mileage.)

4.  Buy used engine and do it myself.  Cost--much cheaper, but many
unknowns.

I have very good mechanical aptitude, and am systematic and painstaking
in my work--but I haven't done any major automotive repairs since I
rebuilt an air-cooled VW 25 years ago. (Did a good job, and VW engine
was still running great five years later when sold.  But obviously a
huge difference between that and a Mercedes engine.)

I've got all the basic metric hand tools, but that's about it.  I'll
have to buy/rent everything else.  I'll fortunately have the time to do
the work essentially uninterrupted--I figure at least two weeks.  Sound
about right?

Should I even consider doing any the work myself?  If so, which approach
would make the most sense?

Thanks.