First of all did you buy the timing kit? Few different brands out there at varying costs,and the parts contained in the kit. Some will only do belt and water pump, some go for the whole nine yards. I believe the flat rate manual calls for it being a 6 hour job. So take that, plus the shop you chose to do the work and add cost of parts and hourly labor rate together and you should have an idea of what your cost should be. Warning though, these are old cars and things can break! So you may have additional costs. 600/700 is an average cost give or take.