You *could* get a color head for your enlarger (if you don't already have one for contrast control in B&W), and one of the RA-4 kits that's still available, and some wonderful Fuji Crystal Archive or Kodak Supra Endura paper (they still make that, right?) and then go to photo.net and search up all the threads where Ron Mowrey (who used to be a chemical engineer for Kodak) and Dan Schwartz discussed color printing at home.
I did all that way back, and successfully and happily printed color medium format in my home darkroom--and the results were very nice. And it actually wasn't that hard at all, once I got the hang of it.
However, that is rather time and labor intensive, and does involve a fairly steep learning curve--and if you don't do a lot of printing, keeping the chemicals fresh is a bit of a bother. So I'm thinking that's *not* the way you want to go.
So, yeah, I'd either send the film (before or after developing) to a lab with a quality reputation for printing and let them do it. Very few of them will actually do it darkroom style nowadays, so they're going to scan your negative and then print it by whichever method you direct. That being the case, and given the variables involved in interpreting color negative film, I'd think that probably asking for high-resolution scans to TIFF (possibly even drum scanning, depending on how large you want to print and how much the image means to you) from your film, which you could then edit and color correct to your satisfaction and send back for printing, would be the way to go.
Many places will do all that for you--but they'll charge you at professional rates for doing so. So personally, I'd think that getting high-quality high-resolution scans done and returned to you for *you* to do the spotting, sharpening, color-correction, etc., would be the way to go. Once you do that, and especially if you've calibrated your monitor to work with the lab's output devices, you should be able to get prints that look exactly the way *you* want them to.
You could also buy an Epson flatbed scanner and one of the betterscanning.com film holders and do your own scanning and editing, and then send *that* to the lab for printing. You won't get super high resolution scans that way, but it'll certainly be good for up to 12x12 inches and possibly a bit more. I used to do that (before I had to sell my scanner to move back to the US) and got highly satisfactory results from it.
Portra is indeed lovely, lovely film. Once you find a method of getting it digitized and printed that suits you, you'll be very happy indeed I'd think with what you get out of it and good quality medium format kit. Best of luck!
