It really comes down to cost and your goals. If this is a $$ decision only, are you building the wheels or are you paying someone else? Can you get the same rims and reuse the spokes? If you are doing the builds, do you have experience and do you consider your time money?
I love building wheels and have done many. I do not consider it a "cost" to me. But I do have to be realistic about the time it takes (and down time for the dining room table - best light and music). If you are skilled building wheels, this could be fun. If this is your first, well I'd advise building a more routine wheel(s) first and do your learning on wheels you don't have feeling s toward. (Granted you picked these up cheap. Still, with a quality build, they will be very nice.)
Maybe a good plan would be to build a lesser wheel or two for the learning experience while riding these on the trainer. Take these on when you feel confident, Yes, in total dollars, you have probably spent the most, but you have picked up a skill that could save some money in the future and give you joy and just maybe save your or someone else's butt/day/ride someday.
This is up to you. We can chirp in with tips like reuse the spokes, use new nipples, etc. but the big question is where do you want to be. For many of us, building wheels is a time-out from life when we have to slow down, block out all else and focus on just what is right in front of us. This can be a real gift.
Ben