Irregardless of whatever parts your epiphone came with. The stock (original parts) that it came with should be sufficient for what its suppose to do.
When you buy a Epi LP, you must already know that it's the tone, controls and feel that you are expecting. Apart from a strat, tele, ibanez...etc, it cater for it's distintive style, so if you have not covered that when you buy it, better chuck it and buy what suits you, serious.
It's in a price bracket, where any major mod or overhaul really outweighs with respect its original value already. But it by itself is a workhorse status, to bring to you extremely good value in performance with regards to it's brand status.
With the above said, I must say the most important issue is that you must not have bought a lemon in the first place. For one thing, it is meant to be a quality instrument but consistency is not it's strong point. So if you have bought a lemon in the first place. Be prepared to fork out maybe half its worth to fix it or just live with the defects.
By defects, I don't mean blemishes or physical damage. Even electrical faults are easier and less costly to rectify. But if the neck has problems to begin with or the intonation cannot be adjusted to acceptable level, you got a problematic instrument.
Hardwares & electronics - tuners, bridge, stoptail, pickups, controls, switches, jacks & wiring. These items comes stock is pretty fair quality, I won't say they are poor quality. What you pay is what you get, my suggestion is that : Don't change any of these unless they really have problem or until they wear out or break.
The pickups are suppose to give you the tone they are suppose to give, so if you are cool with that, no need to upgrade (especially to a same tonal output, just more branded). Else it's an acceptable change to get that special tone you require.
By far I feel the most important thing you need to do is to get it professionally serviced and setup before you do anything else. Get the guitar properly prep for your own needs. This exactly mean the whole fretboard to the intonation and action adjust to your personal need. Normally cost between $40-80 in reputable shops. Get it done by a professional, it's worth it. This is a fixed bridge guitar, So a setup could last a very long time.
Along the way, there will be plenty of minor fixes required to keep it servicable. My experiences are that most of the fixes are pretty cheap anyway. It's only expected, groussing and griping about it is not cool.
Apart from with, the price bracket of this guitar build, makes it a guitar often in the most rugged use situation and ownership. So must give it the due respect it deserve.