Hi Thomas,

First, you don't need to isolate the wheel sets, what would probably best to do is to connect the wheel contacts to one another, this makes that all wheels are connected to the ground. Secondly, a pickup shoe (or two, see below) needs to be added.
Then about converting this model into digital: that's not really easy in a conventional way. I've converted the same model (but AC, non-hamo version) just recently with a great result while using HGH's PCBs, see:
https://www.marklin-user...ault.aspx?g=posts&t=5952

This set of PCBs offers a choice: using two sliders and a mechanism that always switches the one ahead on or using just one slider. The first option is probably best, as it makes that the train will stop in front of a signal, instead of passing it almost completely beforing coming to a hold. I chose to use the first option by the way.

Note that this answer only holds under the assumption that the both models don't differ much besides the electronics in the both heads (which will be replaced completely). If the middle coaches are different compared to the regular 3371, I don't know the answer. Probably HGH knows whether the assumption stated above is right, he's an expert on the 3371 (and other models)

Good luck!

Whilst not an ICE I am in the middle of converting a 216 from Hamo to AC.
I had to change the Bogie where the Slider was fitted to an Insulated one. the Hamo Bogie had no plastic cover and the slider springs came in contact with the Wheel Axles.