R & R 355 speedometer sending unit

I'm about to remove my old speedometer sending unit to replace it with a new one but access looks to be very difficult. At least one of the transaxle oil lines leading up to the heat exchanger is in the way and even if I remove it, the "bolt" size on the sending unit is so big that the only thing I have that fits is an adjustable wrench. Getting that on it in the limited space looks like it will be tough. Even if I were buy the right size metric box end wrench access still looks to be difficult. Whether I remove the oil line or not, does oil come out of the sending unit hole anyway? Does the transaxle oil have to be drained first regardless?

Is there an easier way to do this? Some special tool? I thought about temporarily cutting the electrical connector off so I could get a socket on it and then soldering the two wires back together using some heat shrink tubing to re-insulate the repair. I think this would afford better access but I hate to cut anything that's new like this so I'm asking for some advice from one of you that have done this before.

 

Eurospares. They always have the best prices on everything.

 

Does the transaxle oil have to be drained first? Will oil come out of the hole the sensor goes in when I take it out?