A couple of comments. The mileage you state is no problem for a 300 tdi provided the oil has been changed regularly. I bought one with 124,000 on the clock and did a number of fairly gruelling expeditions with it must have had over 170,000 by the time I sold it and it was still going fine. The engine never failed me once.

Ref injectors I never had any problems.

Ref noise from front end. I have some history here: two failed water pumps and two failed alternators. The bolts holding the water pump in place kept shearing. As you know, the water pump, alternator and power steering pump are all on the same belt which is tensioned by the belt tensioner.

Firstly have a look and see whether the bolts which attach the water pump to the block are intact. Then bend back the belt tensioner and take the belt off and see whether the water pump wheel can move freely and if there is any "play." Seek a mechanic's advise but my recommendation would be to first change the belt, second the belt tensioner and third the water pump and see if it is cured - in that order. It would be worth doing this job yourself as its quite easy and the water pump is a spare I would suggest taking on your trip. Just take your time and follow the Haynes manual.

Ref clutch I would change it before you go on your next trip and get a heavy duty one installed - IMHO the piece of mind make it worthwhile. You may also be getting some slack from the the transfer box and or worn prop shafts though. Again get a professional opinion.