Re: Sentence structure: Yes, there I should've used one.
They mean the same thing. I don't think one is easier to understand than the other, unless the reader is a beginner student in which case the position of "there" might confuse them. However, I do think that the first might be used in a way as to emphasise "there". Let me see if I can explain.
Scenario 1 - I am reading a piece of writing I wrote earlier and I am checking my use of apostrophes. I spot a word where the apostrophe is missing, think about it to check I'm right and then I make a little mark on the paper and say to myself "Yes, I should've used one there."
Scenario 2 - I ask my friend to read my written work with regard to apostrophes. After reading it, she points at a word and tells me she thinks it needs an apostrophe. I check and say "No, that one is fine. It's a plural." then she points to another word and suggests using an apostrophe but I say "No, you're wrong again." This happens several more times until finally she says "Aha! Now this time I'm sure that this one needs an apostrophe" and points to a word. I look and say "Yes, there I should've used one."
Remember - correct capitalisation, punctuation and spacing make posts much easier to read.