No worries mate
Just so you know the genuine balancer is over $1200

From what I have researched the M57d is a pretty bullet proof motor.
BMW put it in all the models
Twin turbo and triple turbo (M50d) the platform for the motor isn't changed much.
There are a few things in the uk like injectors, but it looks like the climate and set up (swirl flaps which we don't have and pre-heater which we don't use here) may cause problems and carbon build up .

I am in the same boat as you.
My wife wants an E70 but now the E53 is worth like $15k its not worth upgrading to get the same car basically.
Especially with all the work I've done.

It sits in the garage most of the week. Wife trains to work.
I have a dual cab and a AE82 twincam (toy) so I hardly drive it bar for family runs.

Plus its super clean , ok a few k's but I love the thing.
And they are a great looking car (when they are clean , have noticed a few early ones around lately looking really shabby)
I have done all the service stuff , all oils. Trans oil twice. About to do a third.
Done the balancer, belts and idlers.
Thermo fan
Got a rail and boost chip from the UK (awesome performance)
Done EGR delete.
LED interior lights and Halo's

So yeah would have to all this to an E70.
Going to wait a couple more years till the E70 xdrive 40D 's come done in price.