If the covers are in good shape you could clean them in a bucket with some fabric softener. Reversing your halyards is a good way to extend their life but if you are using double braid dacron halyards this would be a great time to change to a low stretch line for better sail shaping. Using a low stretch high modulus line allows you to downsize your halyards which reduces friction making sail raising and lowering very much easier.
I switched the stock 7/16" halyards on my boat to 3/8" making sail raising a breeze and reducing halyard stretch which is a real problem for sail shape.