Need some advise...

I found a old SLR camera that my grandfather left me few years back, the exterior has been relatively well kept with the exception of dirty interior. When i look through the viewfinder, i see alot of dirty particles inside. I tried using the cleaning kit to blow the particles out but to no avail.
Mechanism wise, i think it works fine.
Like to find out if this camera is worth the money to do a CLA. If theres any shops that still does CLA for old cameras.
How much would a general cla or cleaning cost me?