We've just moved back into our house after 5 years of having tenants in it and my garden needs a makeover too!

We'll start with treating the whole yard with wettasoil (to improve the amount of water that goes into the ground - you might need to think about putting down claybreaker if you're on heavy clay) then next we'll weed and dig over all the garden beds. Next we'll get a truck load of high grade organic compost - and spread that over the beds. Final layer will be some organic mulch - I'm thinking something like peastraw which is fairly cheap here but will rot down and improve the soil further. We'll think about a more permanent mulch-layer later on once the soil's a bit healthier.

Finally we'll remove all the dead plants, and give a light trim to anything that's likely to survive. By that stage it will be getting on to late summer/early autumn and we can decide what we're going to plant into the gaps we have.

Good luck, enjoy the process!