Did you read my DIY article on timing chain replacement?

http://www.peachparts.com/Wikka/M117TimingChain

The m116's chain is a bit shorter, which means the process will take less time on a 4.2 than it did on my 4.5. It's easy to do, the mini vicegrips I used were like $0.99 each at Wal*Mart. Your guide rails will be plastic though, you WILL want to replace them.