Need replacement lamp for above. I gather the only replacement lamp is the XL-5100? Did google search and found one for $139. Is there a problem ordering them from these sites? Any recommendation or advice appreciated, thanks

Yeah, that's the lamp for your display. The lamp unit from Sony is a bulb in a housing. I don't honestly know what's in the housing except the bulb, but keep in mind that those discount sites generally sell you only the bare bulb without the housing at those lower prices.

Is there a problem ordering them from these sites?

Unless you give the site how do you expect anyone to answer weather the site is a reputable one or not?

You could also look up the site on http://www.resellerratings.com/ & find out if anyone has had problems