2.5 16v Tappet Adjustment? Worse Case Senario?

[Uk Merc Man]

When I first got my car I had the local specialist give it the once over so I could be on top of the maintenance......he picked up on a few bits one of which was he recommended a new timing chain/tensioner set up and also the tappets adjusting.

This was about 2000 miles ago. Over the past 500 miles the symptoms described (poor performance, lumpy idle, slap on start up) are getting slightly worse (although they are still minor I’m being slightly anal here!) so I thought I'd book it in for the tappets adjustment and I'd do the chain and tensioner myself afterwards.

Anyway...they say all things going well 5hrs labour plus misc parts (shims/etc) for the adjustment however....I was wondering what other things "may" need changing?

I remember gearing up to do the same job on a 535i bmw, armed with a screwdriver and a set of feeler gauges. On removal of the rocker cover it became clear I needed a new cam and valve gear!!

Last thing I want is to put it in the garage with a budget of X and find that it needs more work once stripped down and then I cant afford to get the car out the garage!!!

So, what "might" they find.......cams/followers/etc.....

What's the worse case scenario?

I have no reason to think the worse just checking. The car has 100,000 miles with a main dealer history to 89,000. Its well looked after and although the symptoms I described are present they are VERY slight....I just want the car to be in A1 condition.

Any advice appreciated

Thanks

Steve