depends if you want to do this yourself, if you already have a compressor you can get a fairly cheap blasting gun and beads from Machine Mart and from the always useful Ebay.
even if you have it done for you, i'd suggest after blasting to use a rust inhibiter on the chassis before painting.
to paint yourself with cans is not that hard, it's not like doing a large panel like a door where you need to be spending a lot of time polishing, the chassis will be little seen (unless your prone to cornering to fast like Karl
), so a couple of coats or primer with some rubbing down between coats, then 2 or more top coats, again rubbing down between coats with a fine compound paste (bluebell works well), clean and finish of with a clear lacquer.
if you do send the chassis away for blasting, you could try/practice on some scrape metal or cheap baking trays.
regs
Alan