Torquing the rubber bushings and engine mounts can sometimes save replacement. I think its 10mm allen that torques engine mounts from underneath and 19mm wrench for suspension bushings.

Valve seals involve setting each cylinder at TDC while you dismantle the valve train and replace the seals. Special tools include a valve spring compressor and special bent handle valve adjust wrenches. Same as everything on the 240D notso hard to do. But what kinda oil burning are you getting? If it aint less then 1,000 miles per quart I'd leave it alone.

Meanwhile with clutch slave in the works, Its an excellent opportunity to flush hydraulics with fresh DOT 4. Thats something that nobody ever does. MB recommends complete hydraulic flush every 30k miles or so.