Wait, are you absolutely sure that you have to remove the front to access the solenoids?If it were me with that diagnosis, I would ask the shop for a quote to do the variator upgrade & check valves at the same time. When the covers for the cams and front of the engine are removed enough to expose the solenoids, the variator is right there also. So if the variators are not replaced then, all that same labor will have to be paid again if the variators have to be replaced later. The variator parts are not cheap, but the labor is what drives the total cost. Could also depend upon how long you wish to keep the car: it might go quite a way with only the solenoid work before the variators start acting up.
I have a pic of what this much disassembly looks like, if you are interested.