Themostat replacement 2000 elantra

Hi all in group hope all have a happy thanksgiving and christmas and above all a happy new year! I was wandering about changing my tstat in my 2000 elantra 72,000 mi. no mention in owners manual, It seems to warm up a litter slower than usual in this cooler weather and had some tstat failures in other cars stuck closed (overheating) and stuck open (running to cold) why does manufactures not reccommend tstat changes with so many failures of them, it shoud be a recommended maint item in my book. Where is the tstat in this beast, in the lower hose housing, It does't look like its in the upper. Thanks all for any input!