If Windows 11 is currently associated with your MS account, this is probably not necessary. You can transfer your license.
Yes, unfortunately, the power supply will probably need to be migrated, but since you already own a 3070ti, it may be enough. I think you will need at least an 850W power supply.
If you assume that the power supply conversion efficiency in the worst-case scenario is 80%, you will need at least 100/80 = 1.25 times the total power used by the parts, since we think that under typical MSFS load, it is approximately 500W when only the CPU is changed.