Do the heads do anything other than water already-established shrubs? Lots of older systems get by with shrub sprays getting overgrown. If you still need to get water to every plant in an overgrown bed, you will have a few choices, but all of them will make for a more fragile sprinkler system.
The one important consideration for a good drip install is protecting the pipe and components from damage with a thick covering of mulch. The old-school 'textbook' drip install lays out the components on top of bare soil, then adds six inches of mulch atop the pipe and fittings. For most cheaply-done drip installs, emitter tubing is used, and thinly covered, if at all.