Shimano crankset is near end of life, can I use a Tiagra 4700 replacement?
Yes, you can slam the new 4700 chainset straight in there. It should be as simple as that if the ring sizes are the same, though you may need to subtly adjust the front derailleur.
Your other option is to buy a pair of 110bcd 5-arm chainrings from TA, Middleburn, Shimano, etc etc, which is usually nearly as expensive.