totally worth it and IMHO not at all analogous to a vintage car restoration (ask me how I know: a 1968 BMW TI owner )
Since you've already broken the ice with the modern rear rim, if it were my bike I'd opt for something that shifted better than the Triomphe RD, but if you're happy with it, keep it (and don't throw any "old parts" away, store it for later use by somebody who might care to keep it all original). Many components on bikes are not made to last forever, and few bike owners are fanatical about stock originality, especially on a "rider" like this Aelle R frame, as opposed to a 'show bike'...I'd also look after the HS since the "indexing" you mention is not going to get better by itself. Instead of new paint and decals I'd clean and wax it as-is, then just enjoy it for the outstanding ride quality it most probably has.