Scraggman, I guess I should let Peter GT4 answer this but he can add a lot more later on. Peter has done just about every type of maintenance on his GT4 including engine overhaul. To answer the basics of your questions I can tell you if you are not a DIY, Do It Yourself, kinda guy and you depend on the dealer for your services expect to "PAY." A major maintenance with timing belts, tensioners, valve adj, tuning the engine, carbs, timing, points plugs oil, filter change etc. These major services can run anywhere from 3500 upward to 5000 dollars depending on the dealer. If you can DIY, your costs will be much less. Yes the timing belts can be changed without removing the engine. One of the nice things about the 308s.