My dad gave me a nice, older L1500 a few years back. At the time I wasn't even into bass, but after a while I started figuring out some songs and really enjoyed it.
Stopped playing for a while, and then started again and broke a string and stopped again... time passed and I'm interested again, but this time I'd like to see if I can fix up this old L1500.
Don't know how it happened, it's been like this since I got it, but the neck is way warped... It practically looks like 'U' in side view

The strings are way off the fretboard in the middle of the neck.
I went into a music shop tonight to get some strings and tried a fretless for the first time and really liked it too. Also, I'm thinking a 5 string would be definitely be more up my alley to get those really low notes (tried one of those too). A couple of questions for the forum:
1) Is it feasible to convert it from 4 string to 5 string with a new neck? I guess I'd need a new bridge too? Anything else I'd need if this is doable somehow? If so, would the 4 to 5 string conversion leave visible signs like empty drilled holes or anything?
2) How can I fix this bass? Can I send it to G&L for them to modify/fix up? Either adding a 4 or 5 string neck (fretless or not)/bridge... and I think it needs a once over to check the electronics and stuff as I think there's some noise in one of the pots when I play it plugged in with the amp. If G&L wouldn't do it, will they sell me a neck/bridge/parts and then I could take it to a luthier for the install/fix up? Last thing, I'm not 100% sure it even is a L1500, but that's what it looks like to me. How can I tell for sure? I'm still pretty new to bass playing so I will be very grateful for your replies! Thanks