how to change a timing belt or water pump on 3.5 chrysler V-6

You might want to add a couple of things: (1) You should strongly suggest that the tensioner pulley be replaced at this time to renew its bearings (the hydraulic tensioner can be re-used as they seldom give problems). This is an interference engine - it would be a shame to loose it because a $30 part was not replaced and it went bad. (2) You might mention too that if they don't use one of the new-type short pullers for the balancer pulley, they'll have to remove the radiator to make room for the more traditional type of puller. Many auto parts stores rent out the special short pullers.

Engine does not look like the 3.5 in my 2000 3ooM. Is this an older engine? Any difference in belt changing technique?

Yes.

No.