In this sentence, does the meaning stay the same even I change "whether" to "if"?

What is the different between saying "she went on to lose" and just "she lost"?

"She went on to lose" in this context means that even though Meisenheimer won the card drawing and continued campaigning, she ended up losing the election in the end. If he just said "she lost" it would imply that she would have just lost the card drawing and not the election. A more proper way to state this would be "despite winning the card drawing, she went on to lose the election."

What does "good heavens" mean? Is it an idiom to express unexpected surprise?

Yes, it is! "Good heavens" is a way to express surprise towards something. It's a nicer, more appropriate way to express surprise towards something. Ex: Good heavens dear! You scared me. Ex: Oh good heavens. You can't be serious.

In this sentence, does the meaning stay the same even I change "whether" to "if"?

Unfortunately, you cannot use "if" in this sentence. If a sentence is conditional and only presents one option, it is usually okay to use "whether" and "if" interchangeably. However, if a conditional sentence presents two alternatives, you should always use "whether". "Whether" in this context is a conjunction used to show similarity and equality between alternatives. It is not quite the same as saying "if", but it is similar to saying "no matter if". Ex: Anyone can apply for university, whether you are old or young. Ex: You should eat breakfast whether you want to or not. Ex: I don't know if she's going to the party. Ex: He didn't say whether or not he is interested in the job. Ex: Whether rain or shine, we will still have the soccer game.

What does “strap in” mean?

"Strap in" means to secure yourself or someone or something to or into something with a strap, harness, or seat belt. A noun or pronoun can be used between "strap" and "in" or you can simply say "strap in". Ex: Make sure you strap the kids in properly. Ex: I just need to strap in before you start driving. It can also be used to mean prepare yourself or get ready, especially for something shocking or surprising, whether in a good or a bad way. Ex: Strap in, ladies and gentlemen, these financial results are not great. Ex: Strap in for one of the wildest action films of the year!

What does "kickin' it" mean? Does it have the same meaning as "hanging over" or "drop by"?

"Kickin' it" is a slang expression similar in meaning to "hanging out" or "chillin'." The speaker has used it to state that she is not doing anything particularly special, that she is just relaxing and enjoying some leisure time. Ex: A: What are you up to? B: Not much. Just kickin' it at home. Ex: I'm kickin' it at my friend's place.