Yes, you may freely change and wash your ইহরাম garments — the state of ইহরাম is maintained by your intention, not the specific pieces of cloth.
Yes, changing ইহরাম garments is fully permitted and does not affect your state of ইহরাম in any way. The state of ইহরাম is a spiritual commitment entered through intention (niyyah), not a property of the physical garments. You may change to a fresh set of ইহরাম cloths whenever you wish — whether because the current ones are dirty, wet from sweat, or simply for comfort. Many হাজীগণ bring 2-3 sets of ইহরাম garments for this purpose.
You may also wash your ইহরাম garments during the হজ্জ. Use unscented soap or detergent to avoid violating the perfume prohibition. Washing and drying ইহরাম cloths is perfectly permissible. Some হাজীগণ wash their garments in hotel rooms and hang them to dry overnight.
The only requirements when changing are that the new garments must meet the same ইহরাম specifications: for men, they must be two unsewn, unstitched white cloths without any perfume or fragrance. When changing, be mindful of the head-covering prohibition for men — do not accidentally pull cloth over your head while removing or putting on the rida (upper garment). The process of changing should be done modestly, preferably in a private area. Carrying a spare set of ইহরাম garments at all times is মুস্তাহাব, especially during the days at মিনা and আরাফাত.
Source: Ibn Uthaymeen, Majmu Fatawa, section on ইহরাম