How much time do you have on your hands? Will you be building more packs in the future? If not, then get a pro to do it for you, because spot welders are expensive. If yes, then read through The battery builders club to learn everything there is to know about building safe packs + all the tips and tricks to do so.
Personally, even though I know all the safe building guidelines and have the tools to do so, whenever I can, I get someone else to build the battery for me, because it just takes so long unless you do it regularly 