To those who chant this five-sectioned Govinda mantra preceded and followed by omkara he shows his personal form. Therefore, anyone who seeks liberation should constantly repeat this mantra to gain eternal peace.(Gopala-tapani Upanisad, Purva-tapani, text 23)
Every Vedic mantra should be preceded by the omkara. We chant five-sectioned Gopala-mantra preceded by kama-bija which is not a part of five sections, but a seed. How do we understand that? Or nitya-santyai in this contest means mukti, so if omkara replaces kama-bija the effect of the mantra changes? Or should we think that kama-bija is one with omkara as stated in Gopala-tapani Upanisad, Uttara-tapani, text 58? Or should we use both -- omkara followed by kama-bija when chanting Gopala-mantra and Kama-gayatri-mantra?
The GTU speaks about a slightly different way of chanting the Gopala mantra than we do. We chant it together with the other diksha-mantras, while the GTU speaks about doing japa of the mantra alone. In that case, yes, add the pranava both before and after. Otherwise, the answer would be no: if chanting together with the other mantras, you should chant as Guru Maharaja has shown you.