Customise pre-made 3D Models to fit new Game.

I am working on a Turret Defense game that requires some new art work (need enemies, turrets etc.) however as it is an Indie game, we're on a very tight budget. I've decided to purchase pre-made models and found some great ones, just need someone to customise the look to make them unique (and also add on the level 2/3 upgrades for the turrets). There is quite a lot of work to do here, but THIS PROJECT is for: - 1 turret (pre made) to be customised to look unique, - as well as tweaking the model itself to add the level 2/3 upgrade (for instance add more canons/guns) . I want to just check that you are the right person for the job, before handing over the entire workload. So please quote for 1 model customisation only.