Metric Instruments?

I'm trying to do my homework on importing a glider from Germany to the
U.S. Shipping and registration issues shouldn't be a problem, but I'm
curious about the flight instruments. Can I use the metric instruments
in the states? I'm kind of used to metric instruments and I think that
when doing most of my flight calculations, I would prefer to have
metric instruments except for maybe adding a feet altimeter for ATC and
airspace purposes. Does anyone know if there's any problem with this?
I don't really want to have to replace all of my instruments. Any
experience you can share would be very helpful. Thank you.