88-108 is band 2 Broadcast Fm in the UK & Europe, this looks like band 2 1/2 (?) with non hi-fi frequency range and mono with excessive channel spacing and no pre/de-emphasis. Looks like a lost cause to me. But to get back to your question, get hold of a FM broadcast receiver and modify the front end to change the oscillator and RF frequency tuning. If you are stuck with your channel spacing it looks as though you will have to design your own PLL set up if you want to switch from channel to channel.
Frank