from the sounds of the advert its mainly been wear and tear items; ok so its a big initial outlay, but selling now would mean you've basically prepped the car for somoeone else and saved them all the cash. if you've spent it you should enjoy it.
tidy examples are few and far between, so if you've taken one that was a little tatty and cleaned it up then come sale time in the future you will have made selling easier.
with regards to cost of work done personally i feel its part and parcel of owning a higher performance car. its not a fiesta so won't be fiesta running costs. I know you've come from skylines so it should be to much of a shock to the system.
I'm going through similiar expenditures with the XKR at the mo. its not cheap but will be worth it in the end.