"You are wanting a jacket."
Translation:Tha thu ag iarraidh seacaid.
Generally? Yes, sort of. Though some dialects vary. S next to an e or an i (slender vowels) goes to a 'sh' sound, and d next to a slender vowel tends to go to that 'tch' sound which is also very close to a 'j' when at the start of words like 'deànamh'. Next to broad vowels (a, o, u) the s and d tend to be more the sounds you are used to. There's some information about the sounds at https://learngaelic.scot/sounds/index.jsp