Rebuild or new assembled short block?(longer)

[Shotgun28]

Well I only have 90,000 miles, I say only loosely,because some other stangers in here have been going for 200-300,000 miles.I was wondering, I have some oil in one of my spark plug threads, and I am a little nervous, this thing has been babied and well cared for. I got some new heads, but someone said that could make things worse if it is the rings or valve guides, but I cannot afford to do too much after a few recent purchases(just saw the oil in the plug)So now I am wondering if I should wait until late spring, early summer and not put anything on and look into a new short block from Summit or something. But then I am unsure how much all of this would cost a shop to do..I am hesistant to do this on my own.I could remove the intake, heads, etc, to lessen the cost, but I am just trying to see if anyone has done this, should and can I wait, and should I look into a rebuild kit, or new assembled short block. Thanks in advance.
(maybe a compression check or leak down test wouls help me decide. How do you do a compression check, and do I need an air compressor?(sp)
Kevin

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91 LX Convertible Gray on Red B&M Shift improver kit,ASP red alum. underdrive pulleys, Richmond 3.73 gears, 1 5/8 Flowtech long tube Headers and off road h-pipe, Flowmaster 2-chamber cat-back with S.S exhaust, MSD 6A Ignition with coil,Cap and rotor, Taylor Pro wires, K&N 12" conical filter system, Jet stage 2 performance chip and just purchased some GT40P heads, looking at exhaust, Lentech Street Terminator plus on it's way...