I just went from a rough outline to this in 2 hours
Well, I already know one problem with this piece, and so do you!
"How do they think they can do this! We are protected ambassadors under Coalition code 2571 Article 5."
Query: Did you
mean for this guy to come of as an annoying, the-book-is-everything idiot? If not, rephrase to drop out the unnecessary numbers and the like -- e. g. "we're protected ambassadors under diplomatic codes!" or "under the coalition codes!"
"Marcus quiet yourself I do not have much time, for that matter we do not have much time for they will surely come for you next," she said, " Here, take this last data cube and transmit it to the Board of Directors; they must see the disturbing taboo sciences that this culture is researching! It is appalling the things they do to the lower castes and what they do to their own bodies. This data will change everything!"
Trite. It
looks like your aiming for high style, but the fact is high style is A) very,
very difficult to use correctly, and

so overused that even in the hand of a master it comes out clichéd.
"Marcus, shut up! I don't have much time, and they're undoubtedly coming for you now," she said. "Take this last data cube, transmit it to the Board of Directors (note that your use of a semi-colon was incorrect here, you could make a case for either a full colon or a comma however), they must see the taboos this planet is breaking! It is appalling what they do to themselves, this data will change everything!"
Of course, she
is dying -- you might want to consider completely rebuilding that entire paragraph so she's hacking, coughing, breaking in the middle of sentences, using abnormally short sentences, you know, sounds like she's dying...
"Marcus... shut up. I don't have much time, and-" she broke into a spate of coughing, blood spitting from her mouth in a crimson flow. "Take this data cube, the Board must see... These people are monsters! The taboos they break..." she broke down again, blood gushing forth in wet, throaty coughs that sickened Marcus.
"What have you found" Marcus said as he took the data cube and inserted it into the computer
Again, sounds like an attempt at high style, but comes out trite, poorly written -- a more natural form would be "What did you find?".
EMERGENCY – EMERGENCY Hull Breached – We have unidentified intruders entering from engineering
Is this supposed to be the computer speaking? This, and all other "computer" lines, need to be somehow pulled out of the next -- either give the computer a special font, or go ahead and put its text inside quotation marks as well.
Something needs to be done there.
Marcus THINK. this information had to get into Coalition space it had to get into the hands of someone who could get the message to the Directors and that’s when he remembered the small Coalition listening outpost three phase jumps away orbiting a resource asteroid in the Parital field. He plotted the communication address and hit enter beginning the communication upload. Almost there he thought to himself.
A) Instead of "Marcus THINK" try "
Think marcus!" or "Marcus,
think!. Overuse of capitol text is common, and normal, but on forums, and doubly so in stories, its better to use italics to indicate emphasis.

that second sentence is a bit of a run on, isn't it?
"Computer clear the safeties on the reactor and bring this ship to critical overload."
Marcus that is suicide you would surely die in the explosion as well as the entire surrounding four miles around this space port.
OK, maybe the computer wouldn't understand that he's deliberately suiciding right away, but you don't need to establish that for us -- rewrite this part!
"Computer, override saftey protocols and bring the reactor to overload!"
Warning: order will result in complete destruction of this vessel and surrounding environs!
Friends I’ll be seeing you shortly. I am sorry we couldn’t make it through this but hopefully bringing down a some of these bastards and crippling a space port will show them the Coalition is not one to be messed with.
Again, you need to somehow bring this text "out" of the rest to indicate its a thought -- either that, or learn how to push the thought part back
into the rest of the text, but thats a pretty advanced technique that while I've read it often enough, I can't duplicate myself much less help you there.
Also, its a little poorly written.
Friends, Marcus thought, staring into emptiness,
I'm sorry we couldn't get out of here together, but hopefully I'll take some of these bastards with me. And crippling this space port will show them the Coalition is not to be trifled with..
See the difference?
The last thing Marcus saw was a blinding flash of light before he met his endProlo
What
is that line, other than some badly written "tag" line that got typo'd out of existence?