If you only own one property in Spain you do not have to employ a solicitor to deal with your tax affairs.
I'm a non resident home owner and my solicitor has always dealt with my financial affairs but from next year I will be doing them myself.
Each year I pay wealth tax (patrimonia) and income tax (la renta). This is always paid in arrears, this year I paid what was owing for the year 2008. In January 2008 wealth tax was set at 0% so in reality you now only pay (la renta) which is about a 1/3 of what I was paying in previous years.
Every two years I have to fill in a declaration at my bank to prove that I'm non resident in Spain. Some banks charge for this service but I bank with Banco Halifax and it's free.
All my other bills IBI, Electric, Water and Telephone are being paid by direct debit so I don't feel that I should be paying for this one form to be filled in each year. I pay 85e a year for this to be done, 2/3 of what I paid in tax.
I personally think your solicitor is using scare tactics to make you stay with them. You don't say where your property is, there is someone on this forum who will prepare the tax forms for you for 35e. The name of the form escapes at the moment but if you do a search (see prompt at top of page) for wealth tax or la renta all the relevant threads should appear. It's something that has been discussed a lot on here lately....LOL
If you also google la renta that should explain why every non-resident has to pay this tax. Also "You and the Law in Spain" is a worthwhile purchase, most large bookstores have it or you can order it online from Amazon. I think it's by David Seale?