Nice! Yes that's all you need to do, Amethyst should start using it now.

I run strfry, it feels very light on resources: https://github.com/hoytech/strfry

My relay has been mostly idle until now so hard to say what it will look like once more people use it, but so far it needed very little resources: 

https://cdn.satellite.earth/7da1a092d4a569a0e3fe294c257fd36a9c3a871f4467af464a6d524ecd82af4a.png

https://cdn.satellite.earth/536ec31bd672246bf0153f50ed97f42251873a5aa76fea5f8a0817a7194dfa23.png

Ignore the CPU spike as that's a CRON job that updates strfry to the latest build.

Based on this I'd say 1CPU/1GB RAM is probably OK, maybe 2GB of RAM to be more comfortable.