[W126 Coupe] Valve Job?

[Christopher Shurley]

Hey guys--nice to be back on the list.  I have an 88
560 SEC with ~120k miles on it.  The mechanic is
telling me I need a valve job (+ injectors) to the
tune of $5k.  Does this sound right?

Also, if I do it, will I end up spending more later? 
I am just trying to decide whether to keep the car
(its been fantastic) or just sell 'er.

After looking over my costs for the last 6 years I
have owned it, i have spent around $200/mo in
maintenance.

TIA,
Christopher