The month of Dhu’l-Qa`dah (Zilqad) is the first of the Sacred Months to which Almighty Allah has referred in the Holy Qur'¡n. Sayyid Ibn Tawoos defines this month as the month of responding to the prayers in hardships.It is narrated from the Holy Prophet (Peace be upon him and his progeny) that it is recommended to offer this salaat on Sunday in the month of Dhil Qa'da .Reference to this salaat: Mafateeh Al Jinan by Shiekh Abbas Qummi (page 247),Benefits in narrations:-Sins will be forgiven and repentance will be accepted.Allah (swt) will make liabilities to others cleared and when will die with faith (Iman).Religion will be intact. Grave will be widened and enlightened.Parents will be pleased and Allah (swt) will forgive parents and children and will give more wealth.The Angel of Death will be gentle when taking the soul.A'maal the month of Dhil Qa'da It is recommended to do Ghusl & Wudhoo ( only Ghusl is insufficient)Recite a 4 rakat ( 2 X 2) Salaat on any /all Sunday's in Zilqaad month. at any time during the day.In every Unit/Rakat recite : Sura Fatiha/Al Hamd x 1Sura Ikhlass x 3 Sura Falaq x 1Sura Naas x 1  After Salaam 70 times Istigfaar saying,I seek the forgiveness of Allah and I repent before Him.astaghfiru allaha wa atubu ilayhiأَسْتَغْفِرُ اللّهَ وَأَتُوبُ إلَيْهِ.                                                Then onceلاَ حَوْلَ وَلاَ قُوَّةَ إِلاَّ بِٱللَّهِ ٱلْعَليِّ ٱلْعَظِيمِla hawla wala quwwata illa billahil aliyy'al azeemThere is no power and no strength except with Allah, the Most High, the All-great.                                                Then onceيَا عَزِيزُ يَا غَفَّارُٱغْفِرْ لِي ذُنُوبِي وَذُنُوبَ جَمِيعِ ٱلْمُؤْمِنِينَ وَٱلْمُؤمِنَاتِفَإِنَّهُ لاَ يَغْفِرُ ٱلذُّنُوبَ إِلاَّ انْتَYa azeezu ya ghaffarighfir le dhunubi wa dhunuba jameea al mumeneena wal mumnenaati Fa inna hu la yaghfiru aldhunuba illa antaO Almighty! O All-forgiving!(Please) forgive my sins and the sins of all believing men and women, for none can forgive sins save You. so based on the hadith above, can I just do wudu and preform the prayer, or is it wajib to do ghusl for this prayer? 

Ghusl is not wajib
Just wudhu is enough.