1999 SL600 -- ATF leak

[Maximos]

Hi guys. I just bought my 1999 SL600 yesterday. It has 103k miles and has just had the transmission replaced with a unit from an '02 car due to planetary gear failure on the original. He only put 2500 miles on it in the last two years, so I'll probably be looking at a fair share of seals to replace pretty soon.

I drove it home (350 miles) with no problems. This morning, there were no leaks under the car. I drove it an additional ~20 miles and parked it in the garage. I started cleaning up some scratches and stuff and then took it out, only to notice a small puddle of red fluid... the infamous 722.6 fluid. It's coming between the trans and drive shaft. I've attached pictures. Any idea how much this costs, and is it DIY?

Thanks.