If you like, or want to like, working on bikes do yourself a favor and start buying tools. You'll appreciate the quality of Park Tools and you'll really appreciate the money saved compared to paying to have it done for you.
I bought this spanner in preparation for a restoration of a vintage bike. I found that the three-pronged side was just a hair too big for the lockring, so it kept slipping off under pressure. Fortunately the other end hooked on snugly and did the job perfectly. It's a reasonably priced tool I really can't do without-worth every penny.