If you have already booked a ticket to the expo I suppose we had better do something, if not and you have not travelled before then you might be in for a fun time as you are basically doing about as big a trip as you can do in the mainland US and have not planned it very far ahead of time (you can hop on a plane but generally you would want to already know what goes and it might cost you a bit more doing it that way). Likewise depending upon the popularity of the convention and any other events happening in the city on the day (
http://www.travelportland.com/thing...t_date=2013-10-05&event_genre=&event_keyword= says not a lot but as it does not seem to feature this then I am not inclined to trust that site too much) you may have trouble getting a hotel in the city centre.
Going by
http://retrogamingexpo.com/schedule.php
5th and 6th of October (a Saturday and Sunday) opening at 10am though there is something the night before) before ending at 5pm the next day (remember you are also dealing with timezones). I do suggest getting a hotel as staying up for that long is not something I suggest unless you are otherwise experienced at it and roughing it is no fun either.
Do you need a rental car as Portland is big enough to have a halfway functional public transport and the airports and the convention centers are sure to be at least reasonably well serviced (spoiler -- it does). Likewise depending upon your age getting a rental car is a nightmare (if you are 18-20 you will be laughed out of the building or they will start singing "we are in the money", 21 is easier but not by that much and 25 is when it starts getting easier) and seen as you are only wanting it for a few days you probably get a price premium for that. If it is necessary then you can make something happen. Likewise a lot of hotels like you be 21 or older.
Do you have a passport? You do not need one for travel within the US but it can help a bit. Technically you can travel without ID (ish and I would not suggest it if you are not versed in travelling or arguing with people) but a driving license/state ID or some other big form of ID (military being the main one here) will make your life so much easier.
Nearest airport outbound means quite little as not all airports go everywhere and not all airlines are made equal. However I will try and you are bound to be able to change a few times anyway.
Taking us back on topic
http://retrogamingexpo.com/venue.php (always good to check out the parking, hotels, transport situation as every halfway competent website for an event like this will have done something).
Flights from somewhere nearer to you in Virginia going to Portland International Airport (all notable airports have a three letter code and this one is PDX) on the 4th (a Friday) and a hotel on the 4th and 5th with a flight leaving on the 5th preferably later in the day (the convention ends at 5pm but the events largely end at 4:30pm and there is no proper show closer by the looks of things). Travel light though as you should only need two changes of clothes that should not be so bad. I suggest public transport for this and I would probably buy it on the day though if you want to try ordering in advance and collecting there (it might be a bit too late for buying by post) then carry on.
Hotel wise I will try to find you a cheap single bed fleapit with a bed and a shower, again though this close to the day I am not all that hopeful. A quick scan says the motel 6 round the corner is booked up but the one a bit further away will run you just under 140 USD all in.
http://retrogamingexpo.com/venue.php gives you a list of the hotels, I do suggest looking at the hotel's own websites and such like rather than travel sites as it gets odd there and where a travel site says no reservations the actual hotel might have something.
Food wise. Portland is probably one of the better places in the US for food though a lot of that is bars so I hope you are over 21.
Back on flights I have never been to, past or through Virginia so I am not so sure what goes here and I am just reading off a map/list at this point (
http://www.mapquest.com/maps?cat=Airports&state=VA ). Likewise it might be easier to shoot down to Greensboro in North Carolina as that appears to be the bigger airport and is more or less a straight shot down 220 (though the other option appears to be Roanoke and that is a straight shot up 220), both of which are far easier than the runs to Norfolk, Richmond or DC.
A quick search using Greensboro says about 500 USD all in, taxes, fees and everything which is a bit ridiculous so I will try a bit harder.
Redoing the search using Roanoke puts that around 600 USD.
For giggles I tried Norfolk and it was even worse.
This is an expensive gig, I hope you like retro games culture as this kind of money looks like it could buy you said consoles and a flash card for each.
