Are you having to add fluid often? How much? I had a leak under my cadillac from my rack for years and opted to use one of those flat pans to protect my diveway. It worked for me as the leak was minimal and I was planning to sell the car the following year. It's a shame about your rack leaking. I recently had to replace my e30 318i rack because of total failure ... no leaks. Several people helped me out here and the job went pretty easy. If you search "power rack and pump" you will get some useful, critical information on purchasing, warranty, installation, etc... I hope you find it informative. As for your leak, I guess it depends on the rate of fluid loss. If it's high, then you run the risk of running low on fluid between drives and burning out your pump--better to replace it if the leak is out of control, I think. A malfunctioning inner tie-rod end is usually what causes a leak, and will need to be replaced, along with the boots as they are usually compromised in the removal process. One thing I was advised on was, purchasing a rack locally from a standard auto parts store, so I would be able to return it anytime within the warranty period for a newly rebuilt one. I purchased mine from bavarian auto recyclers for about $125.00 including the shipping (1 year warranty)and it works great with no problems or leaks--came with new boots.
I hope the leak turns out to be from a loose hose or something, but if not, it's an easy job.