Must I perform the prayer at its prescribed time and then repeat it later at night, given my suffering from prostate issues and urinary incontinence?

You must pray each prayer at its appointed time. It is permissible for you to combine Dhuhr and Asr prayers, and Maghrib and Isha prayers, performing them at the time of one of them according to the Hanbalis. However, it is not permissible to delay Asr until Maghrib, or to combine all prayers. Clothes becoming impure with urine is not an excuse, as you can wash them or guard them with something and remove it at prayer time. If the difficulty recurs, there is no harm in adopting the view of those who do not consider it necessary to repeat washing and binding for every prayer.