I had a CLK 320 for many years and swapped it for an R231 SL350 5 years ago. The SL is way way better in every respect. More powerful, much better handling, more comfortable, more up to date electronics in every way and more economical.
Currently on vacation in Provence and in 1200 since home have averaged 36mpg.
BTW I’m 79 also, Go for it!!