Headset

Hi everyone.

I am looking to replace my upper headset assembly, as it seems very rusty and I accidentally pulled apart the sealed bearing and lost some of the individual balls. The headset model is the:

'FSA No. 57E Orbit ZS, 1 1/2in lower and 1 1/8in upper sealed cartridge bearings'

I am quite new to the world of headsets. Could anyone let me know which bit I would need to buy to replace:

A) the piece that the three smaller rings on the right form

B) any other bits that I would need to buy with part A to replace the upper assembly

Would I need any specific tools to replace these bits?

Sorry if this is a silly or annoying question!

Thanks