Modifications to the Manley Jumbo Shrimp should be very easy to do to because the main circuit board is on it’s side allowing you to access both sides of the printed circuit board. Don’t be shy to buy a solder gun and an auto-ranging multi-meter then watch YouTube "how to" videos to learn how to solder. I started modifying my own components a couple of years ago with no experience and now Parts Connexion and SonicCraft know me by name.
Start by upgrading the capacitors. Jupiter capacitors and Clarity Cap MR should yield very good improvements for a relatively low budget. Teflon caps are expensive but well worth the cost especially when using them to bypass power supply electrolytic caps (.22uf VCaps make a big improvement to the power supply).