1) How's the insurance? Call your agent. They can give you a quote (which is more helpful than knowing what people in other age groups/locations/marital status/driving record will tell you) Since you asked, I pay about $500/year, full coverage and low deductible. In NJ, I paid about $2k/year for a 20 year old "standard performance" 911. NJ Insurance sucks. Enough said
2) Don't expect the Porsche necessarily be as "FAST" as your SRT-4, especially if you've been hitting the boost bong. The best way to improve a Porsche's performance is by improving the
drivers skill level. Learn to drive the car. If you want 350-400hp, you'd better off looking for a detroit V-8 or keeping your SRT-4
3) Most of the maintenance and usual wear items are not too expensive. What makes a Porsche expensive is avoiding proper maintenance and paying shops (dealer or independent) $100/hr.