Chevy & GMC Vans

I have a 2005 Express G1500. I'm currently filling the steering fluid reservoir with Lucas steering leak fix every time I drive it. It's leaking that profusely. I am on a fixed disability income, so my budget is nonexistent. Is it likely that I need the rack and pinion assembly? It has hydroboost. Mechanic said the part is $1200, which isn't feasible for me. My friend found this part. Am I barking up the right tree? Any thoughts are greatly appreciated.

First, you need to find out where it's leaking from. Since the leak is profuse as you said, it should be easy to spot.
Continuing to put stop-leak products in there will do more harm than good.
Do not buy parts from eBay. You will be very disappointed. I would check Rockauto.