Perhaps try MW Camera Repairs for a second opinion as what you have been quoted sounds extortionate. I have sent both my OM1's to him within the last 18 months for a clean, lubricate & adjust, foam removal from the prism area along with a diode battery modification so the meter will run off an SR-44 battery & the price for each has been £50.
His web site is at MWCameraRepairs
I have also sent a pair of OM2N's to him for CLA's & foam removal & have been very happy with all the work.
Agree with what William Kahn said above about ebay. I picked up both my OM1's off there as spare or repair & the pair of them came to under £40. Have seen working ones go for around £50 on auctions. If you do get another one recommend sending it for a CLA & a defoam at least. Most of them have light seals added around the prism which rot over time & ruin the silvering leaving you with black spots in the viewfinder.