Is it permissible to travel to perform Umrah before Hajj for someone who has not previously performed Hajj, and if so, is he then allowed to perform Hajj al-Tamattu' after this Umrah, and do any changes result from the initial Umrah regarding Hajj al-Tamattu'?

We do not know of any differing opinion regarding the permissibility of performing Umrah (definition) before the obligatory Hajj for one who does not fear an inability to cover the expenses of Hajj. However, whoever fears such an inability should not perform Umrah until he performs Hajj. There is nothing to prevent someone who has performed Umrah from performing Hajj at-Tamattu' by entering into ihram (definition) for Umrah during the months of Hajj, then desacralizing, and then entering into ihram for Hajj from Makkah, and he would be required to offer a sacrifice (hady) for at-Tamattu'. If his Umrah is completed outside the months of Hajj or within them and he does not perform Hajj in the same year, there is no obligation upon him concerning it.