Hey I had some questions related mainly on like how I would make different vehicle seats, guns, and just making a new model into a usable vehicle.

I have never done much on vehicles, all I have done are static props so I know about general exporting with meshex.

if you want moveable turrets, folow this tutorial, if you want moveable treads or takeoff animations, look in the xsi faq-thread.
the other things are set up like any other model. what you need depends on what you want e.g. if you want a pilot, you have to give it a pilotpositionhardpoint, if you want engineffecst, add engineeffecthardpoints and so on.
if you are unsure where to add what, take a look at a shipped vehicle in ultimate unwrap 3d and at its odf, thne you will see which hardpoints are used for what.

if you cant figure out a ceratin thing, ask here of course

Ok here is what I wanted to do.

I have already made the body of the ship/tank. I am attempting to make a ground speeder for racing.

I want two seats/positions for players to sit in, and a toggling view bettween interior and exterior (1st person, and 3rd person as all the stock vehicles have).

So asside from that all I wanted was good engine sounds and two rear after burners, along with giving it more speed in the ODF.

So thats all I can think of, that it needs in order for my project to work. That being said those are the things I would need explained.

then put one null where the first pilot should be another one where the second pilot should be and one null where each afterburner is supposed to be. thats it xsi-wise
the things left are all done through odf-coding. you can use nulls for whatever prupose you want, for playerseats, firepoints, to atach damageffects or engineffects. all you have to do is take an odf of a vehiocle similar to the one you want to create and change the names of the hardpoints depending on how you called them in xsi. when you assigned them correctly you can change the speed, engineeffects and so on..