Think its a 1 1/8th headset, so you need a quill stem in that size. Put a wanted ad up here for one with high rise and see what you get. Black is most popular colour, should get a decent enough one for a tenner or so.
As a commuter it will do a great job I'm sure. Slicks I would advise if mainly on the road or some narrow tyres. But it will be a blast.
Get some updates when you get it all up and going.
I expect after 15 years the tyres are knackered, you will be lucky to salvage the chain, but give everything a good soak in oil and grease everything and see what you can save.
Welcome to the site by the way.