First thing that comes to mind- you have two different nations, different laws in each. Moving a firearm from one to another is called importing, and if you get into THAT it is going to consume a measurable amount of the "rest of your life" you mentioned. Trust me- it is NOT just dropping a gun in the mail.
As far as cost, besides licenses- what is it that you want to DO in gunsmithing? Replace broken parts? Or rebarrel a gun into a custom caliber after you reamed the chamber? Mount and zero scopes, or reblue guns? Each will have a different equipment cost- a good lathe and a good mill are not cheap. Bluing tanks (and ventilation for them) can start to get pricey.
Back in the day, you learned a craft by apprenticing self to a Master in that craft. You may want to consider a PARTIAL version of that- if you can find a senior smith that would like some free help in turn for explaining some of the procedures, kinks and shortcuts.
Now, I am NOT a smith- I am a hobbyist and a collector that does some smithing for myself- but have known some good smiths out there that I learned from.