We still haven't sent a person past our moon, yet we're building nano devices by the trillions.
Humans are problematic creatures, ill suited to high radiation environments and long periods of inactivity, we could get people to Mars but either this is going to be a suicide mission or they'll be coming straight back and even if all goes well they're likely to die from cancer relatively soon after anyway.
What we need is to make small scale mining equipment, a foundry and a fully equipped machinist workshop, small enough to send to Mars at a feasible expense, that'll be the industrial foundation for building the infrastructure required to support an actual human colony, not just a bunch of temporary shelters.
Long-term Mars simply doesn't have the mass to support an Earth-like atmosphere, and I think the core has gone cold too, either way teraforming is just not going to happen without an epic orbital bombardment of materials mined from our system's ore belt, which will devastate anything on the surface and throwing all that material into a gravity well is just an enormous waste. What's far more likely to happen imho is that Mars will become something like the forge world from WH40K, a massive production facility for the equipment we'll need to teraform or strip mine the other planets, and eventually strip mined itself until we carve a death star like space ship out of the iron core.
