Front seals R&R usual price is : >= PhP1k (requires removal of engine accessories, fan, radiator, belts, chains, covers, pulleys, etc.)
Rear seals R&R price : price greater than the front since it requires removal of transmission, propeller shaft, flywheel and clutch assembly while doing it lying down on the garage if mechanic does not have a car lift.

Eto mga nasa isip ko ngayon na parts:
1. Chain (if ever loose). If im not mistaken your engine is TD27 right?
2. Front Seals (crank, cam, balancer if so equipped)
3. Rear Seal
4. Clutch if heavily contaminated with oil
5. Check release bearing if it needs replacement since your mechanic is "already there".
6. Oil pan gasket

Good Seals are cheap pero the R&R labor is not.