With regards to the retirement problem, that's only an issue because people are still thinking like mortals. Were we immortal I'd expect gap years to replace retirement. Many people would choose to live their lives in cycles, retraining every 50 years for a new job / change of scene, getting to a proficient level, then taking a break for a few years until ready (or out of funds) to retrain & start anew. Once they'd done a few cycles people would likely begin to specialise, picking up stuff they'd touched on in the past & taking it to the next level / mixing it with their other skills. The issues then arising are the capacity of the mind (mind rather than human brain since who knows what form it will have taken by this point).
I've assumed that with immortality we maintain physical (if still relevant) and mental fitness, as without those, extending life becomes torturous and pointless, causing people not only to not enjoy their lives, but also to become long suffering burdens on their families, just for the sake of a larger number of sun circuits.
It would make sense to first colonize outer space or, more controversially, sharply control births (or eliminate them altogether), as we would simply run out of space. You need prosperity and an abundance of resources for your cyclic program to work.
