That's a lot of stuff, and if it is OEM Porsche parts then the parts cost alone would be a lot, especially counting all new brakes/rotors/pads.
One way to estimate cost and hours would be to go to
101 Projects Website and look at the various projects that cover the work listed above. Each project has a time range, complexity, and a list of necessary parts. You could add them up and see if the labor/parts cost matches up with your $3000 estimate. (I am not sure of your year but if 2002 or less then you would probably want to do spark plug tubes/O-rings as part of the spark plug service)
I have done all of the items on your list over the last 2 years myself as DIY projects. The tools needed (jack, jack stands, UView airlift for coolant flush, motive bleeder for brakes, specialized wrenches and so forth) plus all the parts came to way less than $3000. But I had a lot of sweating, grunting, and trips to the chiropractor too when it was all said and done.
But I learned a lot and had fun doing it. It is a hobby
And I am not an experienced car person, this is actually the first car I have ever worked on.
That seems a little high, but then I have not recently priced out all the parts either. Or added up the labor. Sorry that I don't have a definitive yes/no but the info above may help you decide.
Good luck!
Steve