As a vinyl player & owner of around 3,000 LP I thought I would add a little more info. I don’t want to rain on your parade, I just wish to share some further insight. When selling vinyl, it needs to be graded, usually visually i.e., mint, NM, VG+, or EX, VG, etc. That said, some defects are easy to see, such as scratches and warps. Others are subtle, such as groove wear from using a cheap or poorly aligned tone arm. History has shown that LPs (1950s to about 1971) tend to play better than they look, and newer LPs (at least until 1989) tend to play worse than they look. Also, not only is actual record graded but so is the album cover.
Technology is far better now then back in the day when it comes turntables & phono cartridges & because of this there is a strong chance that your collection may not sound as well.
I don’t see a huge demand for 78 speed LP, as most new turntables don’t support that speed. 7” 45 RPM records were more of a novelty for the old record players & jukeboxes, you can go on E-Bay & do some searches on “Lot Pricing” for 45RPM, not really a huge demand for these.
Because vinyl has been on an upswing for the last 10-15 years there are numerous facilities worldwide that are pressing reissues of the old titles. Examples of online retailers are Acoustic Sounds, Amazon, Elusive Disc, Music Direct & even Wal-Mart & Target are now selling them.
Genre or music type also weighs in on demand, here are some statistics related to sales by genre for 2018:
Rock 41.7%
Pop 25.6%
R & B 7.9%
Rap/HipHop 6.6%
Stage & Screen 5.7%
Country 2.9%
All Other 5.3%
I’m not going to give any direction on what I think you should do; I believe others have already done that. Best of luck on whatever you choose to do.