There are only a few jobs I would not do myself. This is one of the them. If you use a reputable pro, they will come back and fix it if you have any issues. Although it's really not that bad of a job (provided roof access and roof pitch is not an issue) If you do it yourself, you may find yourself repairing leaks a couple of different times. Someone who does this for a living usually knows minor things to look for and absolutely hate call backs.

If you do not have to replace the current flashing, I think you can do it. Measuring is critical. I would not replace a "bubble" skylight with another plastic skylight (agree with oberon). Glass is the only way to go. And I prefer tape on the curb as opposed to caulk.Good luck!

Whats the size (outside of the curb) measurement here?

Thank you above all. 1, yes, this brown dome skylight is no cost, it was wrapped well in my attic from previous owner, I just teared off wraps. My understanding is the current cracked one has been there at least 15y, For me, it is acceptable if it could make another 15y after replace it.

2, I can go to glass one under reasonable cost ( is glass easily to crack?), but don't know where to order, if the new glass one need totally redoing the frame, it could increase the cost a lot, I hope I could get it done under $500.

3, I don't know any pro around and where to find one, Those guys who replaced my roof said: since the underneath iron frame was nailed in, they could not simply replace it. But, after I checked the structure in and out ( Please see the diagram I drew), it looks to me, I could replace it without touching the iron base frame, so not touching outside flash either, I could only unscrew the outside "retainer frame" then put back with new skylight.

@ East Bay 10 , Tape?, on the diagram, under the flat edge of skylight, there is "rubber strip" around that I could see clearly from inside. I was asking if I need to apply some caulk between skylight and retainer frame, ( please see the diagram ).

@ Windows on Washington Ltd , the size is about 57 X 26 inch, I believe i have to order customized one. I did measure it, I have the exact number at home.

By the way, I went to local Lowes, try to order one, but it was very confusing, they asked a lot of staff, most of them sounds related to the "frame", also the person who did the order also have no idea what it meant. The cost was more than $700, also no idea it was going to work, so I just gave up.

https://www.veluxusa.com/professional/tools/architects/product-sizes

Thank you for your link. I looked the video, I think I will go back to measure all the specs, and if it is possible to use current flash, I could go to order one.

One more thing I just realized, since my skylight is over our guest bathroom, it was lifted up a little bit with condensation gutter inside around the edge, and inside layer is also domed that would let moisture go through the gutter. Since the glass will be flat, will it be matter much ?

Thank you !

@ Windows on Wash..., Could you please tell me if this is going to work for me. My current skylight curb outside size with flashing is 50 X 25 3/4 inches. The Velux skylight product (FCM-2246) is 49 1/2 X 25 1/2, Velux shall build product with some margin, right ? I attached pictures, I hope I could keep current flashing. Thank you so much !

Ordered this one, FCM-2246 with laminate glass. The salesman said it could have maximum skylight clearance"of 26 5/8 x 50 5/8's inch, it shall fit mine. Let's see.

Its probably close and you can rip the curb down slightly to allow for the clearance.

You need to order the flashing kit for and FCM-4646 here though so that the head flashing is for the larger width because you are running width wise.