How to play WOTLK classic or timewalking in retail?

Hello. I am a wow player that has been playing for around a decade casually on and off. I am not a pro, in fact I’m a WOW noob. I know the very basics but I never played a dungeon or raid and I soloed my character. I was playing the new dragon DLC but wanted to play WOTLK i heard its the best and also want to read the book too. I was doing research and unfortunately it looks like i just missed out on the WOTLK classic because it just shut down. I went to “chromie” to start the timewalking dlc . I just traveled to Northrend. Im level 63 but found online that I wont be able to level up past 70 when playing this campagin with chromie. What is the best way to experience WOTLK? I’m assuming the only way now is with chromie. Also should i just make a new character and start fresh with a lower lvl to be able to grind more in northrend? Also as someone who never played a “raid” or a “dungeon” is it still possible to play the full campaign of WOTLK and fight the boss at the end? Thank you in advance for answering me.