O.K It would be really handy if you could give a maximum budget, because you really could spend anything from 500 up to 10,000+.
A couple of things also useful to know still, what is the model of your TV? I assumed an older model but it would be good to know exactly. And I assumed you are from the U.S?
You don't need to be tech savvy to build a PC at all. If you are capable of following instructions to put together a lego set you'll manage fine. But you do need to be willing to spend a bit of time doing watching some Youtube turorials, and potentially troubleshooting you can learn a lot as you go. Time is the key.
Even if you are buying a prebuilt its worth doing some research into parts, PC's do have problems sometimes and if you can do a bit of troubleshooting for yourself you will save a lot of headaches, time, and potentially money.
PCG has a guide for the best pre-built systems not long ago to give you some ideas to start with.
Make one of the best gaming PCs the center of your universe.
Its worth reading the guides for CPU and GPU so you can get a general feel for what you should be looking for too. These are the core parts for your system and you need to know a little at least about them to make a decision
The best graphics cards are slowly coming back in stock.
Fire up your rig with the best CPU for gaming. More cores, more clocks, more of everything that matters.
Other basic tips, 16GB of RAM is enough, 32 GB is more than enough and anything more than that is a waste of money.
Your TV is quite likely only capable of 60hz, therefore 60FPS maximum depending on the model. However 4k is still very demanding on the graphics card. If you wanted to play most new AAA games at maximum settings I would suggest an Nvidia 3070 or AMD 6800 minimum for that purpose. HOWEVER, remember you don't have to play at maximum image quality settings, playing at high or medium is perfectly fine and achievable on cheaper cards too if you dont want to spend that much.
I prefer to have at least around 1TB of SSD storage as games load noticeably faster from them.
Ok, well I hope that wasnt too exhausting. If you have other specific questions let us know! There may be other here who have more specific knowledge of what pre-built companies are better than others, I'm afraid I only know a bit about parts in general.