The disembodied voice inviting us to "Please take your seats for How to Succeed in Business Without Even Trying, had the mood right, if not the exact wording.  That *really* is the vital part of the title.     The charm of this 40-year old musical lies as much in its immunity to the intervening workplace and equal-opportunity laws as it does in the relentless rise and rise of its cunning corporate hero, J. Pierrepont Finch, who, aided only by a thin manual and a thick skin, advances from window cleaner to chairman of the World Wide Wicket Company in the space of a single (albeit long) evening.     This splendidly vivacious staging, the first of this year's series of musicals from the Production Company, is directed with a fine sense of cynicism and good timing by Kris Stewart, who makes the most of the sometimes anarchic and frequently crazed sets of strengths, weaknesses, opportunities and threats that existed long before SWOT analyses took over businesses big and small.     There must have been challenges for Stewart -- not the least of which is the narrow strip of stage flanked by two flights of steps that constitutes Leon Salom's set; the orchestra is upstage -- but he uses the space to its best advantage, avoiding the usual pitfalls of semi-staged performances.     The large cast is dominated by two first-rate performers.  Derek Metzger's impish, inquisitive Finch, who is something of a ruthless corporate climber, has a good heart somewhere on his Brooks Brothers worsted sleeve, and Metzger balances these two sides of his nature with care and craft; John Wood, as JP Biggley, gives a wonderfully full interpretation, with a rollicking gait and basso profondo voice that is particularly effective in his songs.     In addition, Tony Harvey is very funny as the spineless (boneless, really: he is so *floppy*), cringing Bud Frump; and MaryAnne McCormack is a charming Rosemary Pilkington.  Melissa Madden Gray makes a worthy dumb-blonde Hedy La Rue; and the rest of the employees of WWW disport themselves with angular precision (Kelly Aykers' choreography is smartly spot-on) in their various guises.  Guy Noble conducts with real elan, and the State Orchestra responds with gusto.     The real problem, though, with this enterprise is the raw material.  Although the book of How To Succeed is still sharp in its observations about the human condition and office life, the period remains jellified in rose-coloured aspic: the age of all-male executives staring at or touching up all-female secretaries, let alone the musical's only showstopper, The Brotherhood of Man, locates it as firmly in early 1960s New York, when wives stayed at home and their men played around at work, as does Billy Wilder's even more sardonic send-up in his film The Apartment.     Yet, for all this, How to Succeed succeeds by dint of its strong performances, satirical edge and the inevitable progression of its hero.     All these qualities shine forth in this production, even if the piece itself is a trifle too long.  Like most meetings, really.