About the only special tool you need is a 12-pointed bit tool that's driven by a 1/2 socket to remove the head bolts. Fancy versions that match MB specs are available but I find that the PepBoys or AutoZone 4-pack (6mm, 8mm, 10mm and 12mm) for less than $12 fits the bill. I believe that the M103 uses the 12mm bit and you'll have the 10mm when you see the light and upgrade to a car with an OM601/2/3 series engine
You can also spring for the slide hammer arrangement to extract the timing chain guide rail locating pin/s but I've had good luck stacking washers on a high grade bolt to extract the pins. The tool I wish I had is the rod that holds the fan clutch steady for removing the 8mm allen head bolt on the fan. I use some thick wire that eventually catches the notch properly. I've told myself, "this is the last time I'm removing this fan" the last 20 times I've taken off the fan so you'd think I'd learn. Oh, there's a stubby 8mm hex tip tool that fits in the gap between the fan and the radiator. In my 300SE there's enough room to fit an 8mm hex key driven by a 10mm deep socket and breaker bar.
I don't know what tools you'll need to rebuild the transmission.
I still think it's easier to drop the transmission and pull the head than rip everything out.
has a rebuilt 103.983 head for $900. How do you figure it's $300?