As it's written, your sentence is the equivalent of separating two independent clauses with a comma. That's known as a comma splice. While a comma splice is acceptable in some situations, I wouldn't say this is one of them.
There are multiple ways you can deal with this.
1. You can explicitly separate the sentence into two independent clauses with different punctuation:
Your dad's bought a car. That's great.
Your dad's bought a car; that's great.
Your dad's bought a car—that's great.
2. You can turn the second part of the sentence into a clarifying term for the first part with a colon:
Your dad's bought a car: that's great.
3. You can use a comma followed by a conjunction:
Your dad's bought a car, and that's great.
4. You can use a comma but turn what follows it into a nonrestrictive clause:
Your dad's bought a car, which is great.
Note that this leaves the meaning of the sentence ambiguous. It's not clear if it's the fact that he bought a car that's great or if it's the car itself that's great.
5. You can eschew punctuation altogether but make what currently follows it into a restrictive clause:
Your dad's bought a car that's great.
Here, it's clear that it's the car itself that's great, not his purchase of it.
Some of these variations are simply a matter of preference, while others are determined by the exact meaning of what you're trying to convey.
You say "in essence". Do you mean there's more after this sentence, as in...?
Bob will be exposed for his bad deeds and soon will be thrown in jail (example, but you get the point)
In which case there should be a comma separating the two only if the two are complete sentences. Hence
Bob will be exposed for his bad deeds and soon will be jailed.
and
Bob will be exposed for his bad deeds, and soon he will be arrested.
If the sentence just ends where you put the period, then writing "and soon" is either a mistake, or the author means "..., and the above will happen to him soon". In which case, it should be:
Bob will be exposed for his bad deeds, and soon.
Best Answer
Either is ok. Commas indicate a pause. If you want to emphasize the contrast between the two clauses more, add the comma.
By the way you don't need the "to me" in that sentence; it's implied by the fact that the sentence is written in the first person ("I" is the subject).
Advice from the BBC: