Who: Tony Stark AKA Iron Man
Where: Star Wars (actual location up to the author's discretion)
When:
Marvel – At end of Avengers when he's falling through the portal after diverting the bomb and the bomb goes off a tick early and destabilizes the portal, sending him to a Galaxy Far Far Away a little singed.
Star Wars – Either at author's discretion or at the height of a Sith Empire (ie end of Episode 3, start of episode 7, start of KOTOR, some point during SWTOR, etc)
What: Main Quest line – Iron Man believes he has to take over the galaxy in order to find a way back home for reasons up to the authors discretion. Whether this actually works or not is also at author's discretion. Otherwise go nuts and see what how you think Tony Stark would affect the Star Wars universe! (Just please don't leave it following canon. For the love of the log we've all seen the story already, and rewriting the story with just an extra character who may as well not exist except to cause one or two specific changes at the author's discretion (such as setting up certain ships) shows a disturbing lack of imagination and an inherent ignorance of how chaos theory and the butterfly effect works.)
Advantages/Disadvantages – Tony Stark, being extradimensional, does not have midichlorians or what have you. Thus he exists as a void in the Force. As such, while the effects of what he can/has/will do can be seen as a rather chaotic rewriting of the tapestry of life that most any Force User can detect, trying to follow it and pin pointing the source is impossible for all but the grandmasters of the Force, as every other Force user can't detect Tony Stark through the Force since he's a blind spot and most would miss that. Due to this, he cannot use the Force, but something tells me he wouldn't care and would probably figure a way around it, like figuring out how to tap the Force through technology of something since evidently giving Force powers through biological means (like separating Midichlorians out from the blood to inject in another) is canonically impossible somehow, with the effort always failing and causing death. (Sounds like an author copout to me and might not actually be true, but whatever.)
Tony Stark has his armor, albeit it's slightly damaged what with taking a split second exposure to a nuclear space explosion. Doubt the damage is more than superficial, and might've taken out some of his weapons and ability for controlled flight at worst. Luckily for him, due to this, he's not alone, as JARVIS took the opportunity to store a quick and compressed backup of himself when he realized what sir was about to do and prepared for the most unlikely of contingencies, such as Stark getting stranded Log knows where if the portal closes before he can get back. While without hardware and compressed, JARVIS is no better than a particularly intelligent voice assistant. Give him a mainframe, and he'll be back to his full intelligent capacity. Give him access to a internet capable device, and he'll hijack that thing like no one's business. (I find the idea of a Death Star controlled by JARVIS to be highly amusing)
Tony Stark has his brain. His intelligence is almost frightening. Man like that could probably make the universe his bitch if given the opportunity. Well, here's his opportunity. Go wild!