Enquire Now for bulky items, flat rate for other items

[MBuzz]

I'm setting up a store for a client that sells mainly architectural hardware such as handles and tapware. They want to do a flat rate shipping on all orders of handles and taps. I've set that up ok, but they are also planning on selling bathroom vanities. For these they want to show the price but instead of add to cart, have an enquire now button. There seems to be some options that require heavily modifying the code but as I'm using a template, the code is already modified and I don't want to screw this up, plus I'm not that great at code. Thoughts?