I don't think anyone regrets modding. Noone knows where the road ends, but as long as you have fun along the way, that's all that matters.

My car hasn't run 100% since I started modding it, and now my trans is going out. Do I regret it, not at all. Once its where I want it to be, It'll be a stout car and shouldn't break anything else.

Its a long process to the happy point, but if you hang in there, you eventually get there and the results are worth it.