Bowenarrow There wasn't a market for manual box 940s here in the early 1990s. In 93, a 940 SE (turbo) wagon would set you back about 64 grand or so plus on-roads from a dealer, and their target market was people who didn't want to shift gears themselves.
Budget at least $5K in parts for a manual conversion done properly, plus shop labour if someone else is doing it for you (somebody else said about 5 hours shop time, which seems fair IF all the parts are there and ready to go, and if the shop has a hoist). A shop will likely insist you have all the parts ready to go before they start the job, since they can't afford to have a dead car clogging up a hoist.
Parts? There's the gearbox itself, plus tailshaft, plus new clutch & throwout / spigot bearings, plus LH2.4 flywheel, plus R&R of pedal box, plus clutch hydraulics, plus rewiring for reverse lights, / start inhibit / overdrive and relay / etc, plus the gearbox crossmember and rubber mount(s), plus getting all the RHD trim bits from the UK so the inside doesn't look crap and get noisy. It all adds up.