Since when did gu dòigheil mean 'really well'. I have never heard that and nor have the dictionaries I have looked in. AFB has
1 fully satisfied 2 all right 3 right, correctly
Dwelly does not have it but for dòigheil he gives
1 Systematic. 2 Well-arranged well-appointed. 3 Good-tempered. 4 Convenient. 5 Hopeful, confident. 6†† Accommodating. 7* Decent. 8(DC) Suitable — Uist. 9(DC) Tradesmanlike — Uist. 10 In good trim or condition. 11 Well off, in good circumstances
None of these has the sense of 'really well'. I was taught it meant fine, although it was not used in the dialect I learnt.