And you think the upgrade to a 430 would bring you more reliability ??? and less on-going costs !
If the cambelt was changed less than 100,000 miles / 10 years ago then it really doesn't need changing yet and the rest is probably just fair wear and tear that will cost you less than the cost of the upgrade.
But there you are, deep in your heart you really know the answer already, and if you want to scrap the dear old lady and take on heavier maintenance and servicing costs and capital costs out of your pocket then, well, go ahead and sell her for a pittance to the breakers ! Watch her cry !!!!
It will be sad. She should be good for at least another 150,000 miles yet.
Malc