Depends if you are going to change full exhaust or slip on only. Your post suggests the whole lot.
If you change the lot then yes your bike will benefit from a retune, but you may well find it runs ok for your purposes - it just may lose a few horses. It's mainly when you mess around with air filters etc. that you need to consider adjustments.
If you just put on a slip on there is usually no adjustments needed.
Re-tuning isn't a big issue and most garages, unless you have the equipment yourself, will do it in about half an hour.
Off the Inazuma Topic - I brought a tuner to re-tune my bike following an exhaust mod and high performance air filter fitting, following the re-tune the bike runs really sweet and has noticeably more acceleration so it may be worth investing in having it done?