his mechanic or technician is either severely inexperienced or extremely useless, the power steering system in a toyota corolla is extremely easy. And about replacing the seals in the rack. I have done it - it takes common sense approach and a few special tools which are very cheap too.
special tools required are
1 - super long awl to pull out center seal
2 - cut up 1.5 litre pepsi bottle to install center seal
rest is common sense approach and some assembly lube like vaseline or STP engine oil additive.
the return line are simple low pressure lines (if leaking then replace with correct hydraulic purpose pipe, not regular rubber pipe) The pressure line is crimped and can be redone if required. Use ATF in the power steering system and bleed out all air. It will work nicely and sweetly.
Throwing junkyard racks at a car to make it work is downright funny and comical. Find better mechanics (they will be expensive than your regular one) and follow correct repair procedure. If you work on the principle of shooting parts at your car then buy a brand new rack from toyota.