It's not a big deal how you pronounce the name. And how we pronounce different names depends more on all the different accents in sweden. The letters Y and J are very simulare, I think it is the vocals you'll change in many names.
For example, in the name John, the O is pronounced more as the second O in "com'on" in english(?) and would sound more like the O in the english word "on" in swedish.. Don't know if you see the difference here. hehe. It's easier if you actually hear a swedish person say these names for you, so that you can decide if there are any differences.