Growing black blob

We bought our Toshiba just over a year ago (warranty ran out 2 months ago). The bulb blew twice and was replaced for free. Things have been ok for a while, but now there are dark gray/black blobs on the bottom of the screen (they are transparent). They started as two and grew together and now there is another one growing on the other side. You can also see where these blobs are when the TV is off. It reminds me of ink that is bleeding behind the screen. Any idea what this is? The repair department of the place where we purchased the TV said they'd have to get it into their shop to see it, but it's probably the light engine, which is quite expensive. From what I've read on this post and others, light engine problems seem to be described differently. We are willing to take the TV apart, since the warranty is up anyway if you have any suggestions on where to look and what to look for. Otherwise, if you could give me a range of cost so I know if I'm getting a decent price. I'd appreciate any help you may give. Thanks!