It sounds like you may have two issues here, the first is the hard start problem. Ford has a pcm update out that addresses 2005 taurus hard start concerns, I think some of them were under a recall., but I would have to check your VIN to verify that.
Second have you had the battery tested, Onyour ford's if the instrument cluster looses voltage then the cluster will perform a reset mode, that may bbe why your guages are acting up.
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When you go to the dealer just tell them you just want the pcm updated. They will probably try to sell you diag, which cost around $100 dollars. I recommend you decline and just get pcm updated this procedure should run between $80 and $100 dollars.