I used Village Cleaners to clean and perserve my wedding dress. The place is really nice, clean and the staff is easy to talk to. They explained the difference between the different wedding cleaning options. You'll need to decide if you want your dress cleaned, hung, pressed and/or preserved. I'm sure I did standard cleaning and preeserving and I'm pretty sure the prices were reasonable -- it was definitely more than cleaning a suit and definitely less than the cost of my alterations (which were done elsewhere, but Village Cleaners does alterations also).
Overall Village Cleaners is nice. Sometimes they are a bit pricey for everyday items, but I always use them for nicer pieces, because I know they will take care of them. When it came to my wedding dress, the price was better than I expected.
Regarding the comment on timing: It seems like they just clean the dress, press it and put it in an acid free box (or two). I think you are supposed to get it re-cleaned and preserved every 10 years so if it hasn't yellowed, I don't think it is ever too late to get it cleaned.