You might need to purchase a set of removal keys for the old head unti but I managed to remove the one in my 2001 Brava SX with a pair of kitchen knives to depress the springs. That was harder than actually fitting the new stereo!
The standard size stereo I was putting in fits snugly into the fascia and the fascia snugly into the dash. The iso leads fit together comfortably without any forcing - the one end fit perfectly into the the iso lead on my stereo and the other perfectly to the connection blocks from my Fiat, no need to cut or rewire anything which I was a bit concerned about as I have no clue with that sort of thing and the aerial adaptor slotted in first time and is in there nice and tight.
For the money I can't fault this product. The fascia is a little bit flimsy but these kinds of things always will be and it's not due to cheap design as they are all pretty much the same. Much better value than Halfords who are asking £14.99 for the Fascia alone, £1.99 for the aerial and god knows how much for an iso adapter to fit the blocks on the Fiat. Great service too, delivered the day after it was sent out via standard shipping.