Costs of parts are different in different countries, I only state my costs.
On my 240 Turbo, I recently replaced the three front seals and also the
gasket for the panel which holds the two lower seals. Parts cost me
about US$37. A timing belt costs about US$13. This was in Sweden, where
I happen to live. Since Volvo has a large market share here, I think
parts are reasonable. The large share creates a market for non-orginal
suppliers.
My prices are for Volvo original parts. The job took me a few hours,
since I did a lot of cleaning. To get space to work, I drained the
coolant and removed the cooler, which probably was not necessary. As a
minimum you need to remove the fan, the V-belt pulleys and the
transmission belt cover. Then you must remove the timing belt and the
timing belt pulleys to get to the seals. An experienced mechanic can
probably do this in 2 hours, including cleaning things up. Replacing the
belt takes no extra time/effort if you do the front seals.
Now this was for front seals on a "classic Volvo" (200/700/900) four
cylinder. The rear seal is a bit harder (removal of drive
shaft/gearbox/clutch/flywheel).
--
Gunnar
240 Turbo Wagon '84 200 K Miles
940 Wagon '92 150 K Miles
on Swedish roads