is it a hard job to do or should i just get it done at a garage?

Its not very hard to replace shocks/springs. I dont recomend replacing them if you dont have the proper spring compressor, not the $10.00 kind.

If you have no experience with this, for Gods sake go out and get the book and read it. It you don't think you are capable then dont. I have seen far too many people f-up their rides from installing suspension parts incorrectly. Honestly, its not all that complicated though.