You can go with asus prime B450M-K,it is available for same price as msi b450pro-m2 at mdcomputers.Don't buy gigabyte psu or mobo,their psu is not good quality & any gigabyte amd ryzen mobo is not worth considering unless it is the only option.
Any local pc shop should be able to assemble at reasonable rates(below 1k) else ask some friend who has this knowledge to do this for you.Only tricky thing is installing cpu stock cooler & processor,rest all is simply connecting wires & screws(any 20-30min youtube video is more than enough).