I have a collection of OM-1 and OM-2 bodies, all dating back to the mid-late 1970s. Your price sounds fairly good to me. My expectation is that, unless I purchased a used body from someplace like KEH or a private seller whose maintenance/repair work I trust, I'm going to have to have it CLA'ed, probably sooner rather than later.

For an OM-1, you will need to use a replacement battery, most likely, unless the mercury batteries are still available in England. The adapter identified above is good (and necessary: a difference of a few 1/10s volt can make the meter readings screwy), but spending $30US on the adapter puts you 30% of the way to the coast of a CLA at someplace like Camtech (http://www.zuiko.com/) where the CLA will permanently correct the OM-1 so that an adapter is not necessary.

If you can afford it, I would get the whole thing checked out and timed, seals replaced, meter aligned, battery changed-over and be done with it. When I have violated my rule, and not gotten it done, I usually regret it. (BTW, I have no connection with Camtech other than the fact that I have used them and they have one of my OM-1s even as we speak - - my oldest from 1977).

...More free advice... and worth every penny.