The rear shocks are as easy to replace as you can get.
Open boot, remove suspension top mount cover, unscrew nut. Jack up rear of car, remove wheel, unscrew lower strut bolt and remove strut - Easy.
I'd never dream of taking my car to the garage for such a simple task, so no, I can't recommend any nearby garages.
The units are not serviceable/refillable to my knowledge - unless someone else knows otherwise...