It kind of depends on the fault, the cost to repair, and whether you use 3D still.
Have a look on Google and Youtube for faults your model of set. If it's something well known such as a dead board, and you fancy a bit of a go yourself at swapping it out, then you might get away with a repair for £30-£70.
The chances are that any new replacement set will be a UHD 4K product. There really isn't that much of a choice left in Full HD sets any more; or not of any quality at least. UHD 4K is new tech, but that can be a double-edged sword, particularly if you still watch a bit of Standard Def. It's also the case that budget UHD 4K TVs can look like a backwards step in general picture quality compared to the TV they're replacing. Avoid the cheaper brands and stick to the Samsung, Sony, LG, Panasonic sets in the middle of each manufacturer's range. The rest of what's in the market is mostly just badge engineered stuff.
If this or any other posts helped you then pay the authors the compliment of hitting the thanks button. It shows your appreciation and marks the reply for those looking for answers in the future.