Changing the springs on a MINI isn't any different than any other car. The main part is the right tools to disassemble the strut. An open socket and the correct allan wrench. Either way you'll need an alignment afterwards. Are your TSW springs the new ones from WAY or use ones? If they are the new ones I'd love to hear how you like them after you get them on.
Update on this issue: I checked this car out for the oil problem, looked to be too end and turbo using oil. I had the customer take it to MAG, and the confirmed the turbo and valve cover. No idea why Best thought a timing chain for $3500 would fix this issue. This is my opinion but i will never send anyone to Best again. Hopefully Anson will open his own shop one day.
Wouldn't Anson be the one diagnosing the issue? I have had one issue with Best, and he made it right - beyond my expectation. I continue taking both MINIs there, and trust Anson will do great work.