Hi,how hard is it to install performance headers in a 1990 5.0lx?I am a noob to engine bolt on HP but am good with my hands.It looks easy enough to do but worried about at how hard the bolts on stock headers are going to be to unsrew off engine block and the one side were it looks like i have to take other engine parts off to get at header.I have off road h-pipe and 2 chamber muffers system now.How much more HP will i gain with headers?How many hours avergae would i need to install headers?Would it be better just to take it to a shop and hve it done? Thx.