Even if you had to buy some tools it would save vs. the time and labor costs. If you can manage it. If you're doing it in a parking lot, then you're a bit more limited. But I replaced even the lower arms of my car (almost 300k now) a while back, and I only had to buy a large torque wrench to make sure it was on well. But I had a covering parting spot and some time... so, it depends.

Always buy the full assembled of parts, not just bushings or other joints.