Some festivals I would reccomend are
Siggraph
Ars Electronics (very highend with prize money)
Spike And Mike (gross, weird animation)
ResFest (wide range of techniques and genres)
Rotterdam Film Festival
Chicago Undergound FIlm Festival (low brow low budget)
Most Festivals have some sort of entrance fee so you want to make sure that the festival is reputable as there are some that are just in it for the profit.
I would not say that it is expected or a requirement to have a 35mm print to get intoan animation festival.. usually only big animation studios go that route and you are not a big studio. The rates for printing vary and are usually lower in high volume (hours as opposed to minutes). You could look at www.efilm.com for some high rates. You also have to consider getting your sound to film which is another ball of wax to deal with. Really if you want Hi-Resolution then consider Hi-Def.. I think most festivals can accomodate that and it will cost you alot less trouble.
I don't think any festival expects you to be there.. I guess if you win an award they'll let you know so that you can be there if you wish. If you spent $10 grand or more printing your film I can imagine you can afford a plane ticket.
There is a book or books on the subject of submitting to festivals. The biggest tip is to manufacture a thorough press kit. For some festivals this includes making slides of frames from the film for reproduction in their advertisments and catalogs.
Some festivals have an exclusive submission policy.. I think this is a load and are to be avoided.. basically this means that if your piece is accepted into their program that it cannot be shown in another festival at the same time.
The next thing you need to do is to make the aniamtion. You may wish to make note of when your target festivals have deadlines and work that into your schedule. Some festivals will allow you to submit a work in progress and let you finish by an extended deadline.
Consider hiring a professional sound designer or composer to score your soundtrack. Canned music usually sounds canned and not all animators are great sound designers so leave that to somebody who specializes in it..besides you'll be too busy trying to finsh the animation. Likewise I would have somebody else edit the piece. Show the storyboards to objective viewers and get feedback. Make an animatic so that you know what the timings are before animating and get an editor to help you with this.
Goodluck