I had a Remington .375 H & H shoot patterns rather than groups, so I ordered a CZ 550, .375 H & H. It shot fantastic just out of the box. I didn't have time to glass bed it, just scope it up with CZ rings, slap a Leupold 3X9 on it, zero and practice with about 300-400 rounds, and off to RSA. Now I have the time, what am I going to do to "improve" it? Nothing, but shoot and enjoy!

Do a search - there's been plenty written about CZ scope mounts on this site - to cut along story short the CZ factory rings are reasonable quality albeit a bit high, and the best available are Talleys imo.
Good luck
charlie

I plan to buy a new CZ 550 American in .375 H&H. What modifications should I expect to have to make to it, besides the obvious epoxy bedding job in order to strengthen the stock against recoil? Are there weak or plastic parts that should be replaced with better aftermarket parts? Will I probably be dissatisfied with the trigger, and want to replace it?

Lots of threads on that pretty recent. Do a search with CZ in the subject heading and you'll come across them soon enough.

The trigger on mine felt creepy, until I adjusted the "before" movement to zero (turn the adjustment screw all the way to the end), and now it as crsip as any trigger I have.

Frans